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        <dc:title>On The Generation Of Animals</dc:title>
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        <alex:sortTitle>On The Generation Of Animals</alex:sortTitle>
        <alex:fullText><![CDATA[                                     350 BC

                          ON THE GENERATION OF ANIMALS

                                  by Aristotle

                           translated by Arthur Platt

                              Book I

                                 1

  WE have now discussed the other parts of animals, both generally and
with reference to the peculiarities of each kind, explaining how
each part exists on account of such a cause, and I mean by this the
final cause.

  There are four causes underlying everything: first, the final cause,
that for the sake of which a thing exists; secondly, the formal cause,
the definition of its essence  (and these two we may regard pretty
much as one and the same);  thirdly, the material; and fourthly, the
moving principle or efficient cause.

  We have then already discussed the other three causes, for the
definition and the final cause are the same, and the material of
animals is their parts of the whole animal the non-homogeneous
parts, of these again the homogeneous, and of these last the so-called
elements of all matter. It remains to speak of those parts which
contribute to the generation of animals and of which nothing
definite has yet been said, and to explain what is the moving or
efficient cause. To inquire into this last and to inquire into the
generation of each animal is in a way the same thing; and,
therefore, my plan has united them together, arranging the
discussion of these parts last, and the beginning of the question of
generation next to them.

  Now some animals come into being from the union of male and
female, i.e. all those kinds of animal which possess the two sexes.
This is not the case with all of them; though in the sanguinea with
few exceptions the creature, when its growth is complete, is either
male or female, and though some bloodless animals have sexes so that
they generate offspring of the same kind, yet other bloodless
animals generate indeed, but not offspring of the same kind; such
are all that come into being not from a union of the sexes, but from
decaying earth and excrements. To speak generally, if we take all
animals which change their locality, some by swimming, others by
flying, others by walking, we find in these the two sexes, not only in
the sanguinea but also in some of the bloodless animals; and this
applies in the case of the latter sometimes to the whole class, as the
cephalopoda and crustacea, but in the class of insects only to the
majority. Of these, all which are produced by union of animals of
the same kind generate also after their kind, but all which are not
produced by animals, but from decaying matter, generate indeed, but
produce another kind, and the offspring is neither male nor female;
such are some of the insects. This is what might have been expected,
for if those animals which are not produced by parents had
themselves united and produced others, then their offspring must
have been either like or unlike to themselves. If like, then their
parents ought to have come into being in the same way; this is only
a reasonable postulate to make, for it is plainly the case with
other animals. If unlike, and yet able to copulate, then there would
have come into being again from them another kind of creature and
again another from these, and this would have gone on to infinity. But
Nature flies from the infinite, for the infinite is unending or
imperfect, and Nature ever seeks an end.

  But all those creatures which do not move, as the testacea and
animals that live by clinging to something else, inasmuch as their
nature resembles that of plants, have no sex any more than plants
have, but as applied to them the word is only used in virtue of a
similarity and analogy. For there is a slight distinction of this
sort, since even in plants we find in the same kind some trees which
bear fruit and others which, while bearing none themselves, yet
contribute to the ripening of the fruits of those which do, as in
the case of the fig-tree and caprifig.

  The same holds good also in plants, some coming into being from seed
and others, as it were, by the spontaneous action of Nature, arising
either from decomposition of the earth or of some parts in other
plants, for some are not formed by themselves separately but are
produced upon other trees, as the mistletoe. Plants, however, must
be investigated separately.

                                 2

  Of the generation of animals we must speak as various questions
arise in order in the case of each, and we must connect our account
with what has been said. For, as we said above, the male and female
principles may be put down first and foremost as origins of
generation, the former as containing the efficient cause of
generation, the latter the material of it. The most conclusive proof
of this is drawn from considering how and whence comes the semen;
for there is no doubt that it is out of this that those creatures
are formed which are produced in the ordinary course of Nature; but we
must observe carefully the way in which this semen actually comes into
being from the male and female. For it is just because the semen is
secreted from the two sexes, the secretion taking place in them and
from them, that they are first principles of generation. For by a male
animal we mean that which generates in another, and by a female that
which generates in itself; wherefore men apply these terms to the
macrocosm also, naming Earth mother as being female, but addressing
Heaven and the Sun and other like entities as fathers, as causing
generation.

  Male and female differ in their essence by each having a separate
ability or faculty, and anatomically by certain parts; essentially the
male is that which is able to generate in another, as said above;
the female is that which is able to generate in itself and out of
which comes into being the offspring previously existing in the
parent. And since they are differentiated by an ability or faculty and
by their function, and since instruments or organs are needed for
all functioning, and since the bodily parts are the instruments or
organs to serve the faculties, it follows that certain parts must
exist for union of parents and production of offspring. And these must
differ from each other, so that consequently the male will differ from
the female.  (For even though we speak of the animal as a whole as
male or female, yet really it is not male or female in virtue of the
whole of itself, but only in virtue of a certain faculty and a certain
part- just as with the part used for sight or locomotion- which part
is also plain to sense-perception.)

  Now as a matter of fact such parts are in the female the so-called
uterus, in the male the testes and the penis, in all the sanguinea;
for some of them have testes and others the corresponding passages.
There are corresponding differences of male and female in all the
bloodless animals also which have this division into opposite sexes.
But if in the sanguinea it is the parts concerned in copulation that
differ primarily in their forms, we must observe that a small change
in a first principle is often attended by changes in other things
depending on it. This is plain in the case of castrated animals,
for, though only the generative part is disabled, yet pretty well
the whole form of the animal changes in consequence so much that it
seems to be female or not far short of it, and thus it is clear than
an animal is not male or female in virtue of an isolated part or an
isolated faculty. Clearly, then, the distinction of sex is a first
principle; at any rate, when that which distinguishes male and
female suffers change, many other changes accompany it, as would be
the case if a first principle is changed.

                                 3

  The sanguinea are not all alike as regards testes and uterus. Taking
the former first, we find that some of them have not testes at all, as
the classes of fish and of serpents, but only two spermatic ducts.
Others have testes indeed, but internally by the loin in the region of
the kidneys, and from each of these a duct, as in the case of those
animals which have no testes at all, these ducts unite also as with
those animals; this applies  (among animals breathing air and having a
lung)  to all birds and oviparous quadrupeds. For all these have their
testes internal near the loin, and two ducts from these in the same
way as serpents; I mean the lizards and tortoises and all the scaly
reptiles. But all the vivipara have their testes in front; some of
them inside at the end of the abdomen, as the dolphin, not with
ducts but with a penis projecting externally from them; others
outside, either pendent as in man or towards the fundament as in
swine. They have been discriminated more accurately in the Enquiries
about Animals.

  The uterus is always double, just as the testes are always two in
the male. It is situated either near the pudendum  (as in women, and
all those animals which bring forth alive not only externally but also
internally, and all fish that lay eggs externally)  or up towards
the hypozoma  (as in all birds and in viviparous fishes).  The
uterus is also double in the crustacea and the cephalopoda, for the
membranes which include their so-called eggs are of the nature of a
uterus. It is particularly hard to distinguish in the case of the
poulps, so that it seems to be single, but the reason of this is
that the bulk of the body is everywhere similar.

  It is double also in the larger insects; in the smaller the question
is uncertain owing to the small size of the body.

  Such is the description of the aforesaid parts of animals.

                                 4

  With regard to the difference of the spermatic organs in males, if
we are to investigate the causes of their existence, we must first
grasp the final cause of the testes. Now if Nature makes everything
either because it is necessary or because it is better so, this part
also must be for one of these two reasons. But that it is not
necessary for generation is plain; else had it been possessed by all
creatures that generate, but as it is neither serpents have testes nor
have fish; for they have been seen uniting and with their ducts full
of milt. It remains then that it must be because it is somehow
better so. Now it is true that the business of most animals is, you
may say, nothing else than to produce young, as the business of a
plant is to produce seed and fruit. But still as, in the case of
nutriment, animals with straight intestines are more violent in
their desire for food, so those which have not testes but only
ducts, or which have them indeed but internally, are all quicker in
accomplishing copulation. But those which are to be more temperate
in the one case have not straight intestines, and in the other have
their ducts twisted to prevent their desire being too violent and
hasty. It is for this that the testes are contrived; for they make the
movement of the spermatic secretion steadier, preserving the folding
back of the passages in the vivipara, as horses and the like, and in
man.  (For details see the Enquiries about Animals.)  For the testes
are no part of the ducts but are only attached to them, as women
fasten stones to the loom when weaving; if they are removed the
ducts are drawn up internally, so that castrated animals are unable to
generate; if they were not drawn up they would be able, and before now
a bull mounting immediately after castration has caused conception
in the cow because the ducts had not yet been drawn up. In birds and
oviparous quadrupeds the testes receive the spermatic secretion, so
that its expulsion is slower than in fishes. This is clear in the case
of birds, for their testes are much enlarged at the time of
copulation, and all those which pair at one season of the year have
them so small when this is past that they are almost indiscernible,
but during the season they are very large. When the testes are
internal the act of copulation is quicker than when they are external,
for even in the latter case the semen is not emitted before the testes
are drawn up.

                                  5

  Besides, quadrupeds have the organ of copulation, since it is
possible for them to have it, but for birds and the footless animals
it is not possible, because the former have their legs under the
middle of the abdomen and the latter have no legs at all; now the
penis depends from that region and is situated there.  (Wherefore also
the legs are strained in intercourse, both the penis and the legs
being sinewy.)  So that, since it is not possible for them to have
this organ, they must necessarily either have no testes also, or at
any rate not have them there, as those animals that have both penis
and testes have them in the same situation.

  Further, with those animals at any rate that have external testes,
the semen is collected together before emission, and emission is due
to the penis being heated by its movement; it is not ready for
emission at immediate contact as in fishes.

  All the vivipira have their testes in front, internally or
externally, except the hedgehog; he alone has them near the loin. This
is for the same reason as with birds, because their union must be
quick, for the hedgehog does not, like the other quadrupeds, mount
upon the back of the female, but they conjugate standing upright
because of their spines.

  So much for the reasons why those animals have testes which have
them, and why they are sometimes external and sometimes internal.

                                 6

  All those animals which have no testes are deficient in this part,
as has been said, not because it is better to be so but simply because
of necessity, and secondly because it is necessary that their
copulation should be speedy. Such is the nature of fish and
serpents. Fish copulate throwing themselves alongside of the females
and separating again quickly. For as men and all such creatures must
hold their breath before emitting the semen, so fish at such times
must cease taking in the sea-water, and then they perish easily.
Therefore they must not mature the semen during copulation, as
viviparous land-animals do, but they have it all matured together
before the time, so as not to be maturing it while in contact but to
emit it ready matured. So they have no testes, and the ducts are
straight and simple. There is a small part similar to this connected
with the testes in the system of quadrupeds, for part of the reflected
duct is sanguineous and part is not; the fluid is already semen when
it is received by and passes through this latter part, so that once it
has arrived there it is soon emitted in these quadrupeds also. Now
in fishes the whole passage resembles the last section of the
reflected part of the duct in man and similar animals.

                                 7

  Serpents copulate twining round one another, and, as said above,
have neither testes nor penis, the latter because they have no legs,
the former because of their length, but they have ducts like for on
account of their extreme length the seminal fluid would take too
long in its passage and be cooled if it were further delayed by
testes.  (This happens also if the penis is large; such men are less
fertile than when it is smaller because the semen, if cold, is not
generative, and that which is carried too far is cooled.)  So much for
the reason why some animals have testes and others not. Serpents
intertwine because of their inaptitude to cast themselves alongside of
one another. For they are too long to unite closely with so small a
part and have no organs of attachment, so they make use of the
suppleness of their bodies, intertwining. Wherefore also they seem
to be slower in copulation than fish, not only on account of the
length of the ducts but also of this elaborate arrangement in uniting.

                                 8

  It is not easy to state the facts about the uterus in female
animals, for there are many points of difference. The vivipara are not
alike in this part; women and all the vivipara with feet have the
uterus low down by the pudendum, but the cartilaginous viviparous fish
have it higher up near the hypozoma. In the ovipara, again, it is
low in fish  (as in women and the viviparous quadrupeds),  high in
birds and all oviparous quadrupeds. Yet even these differences are
on a principle. To begin with the ovipara, they differ in the manner
of laying their eggs, for some produce them imperfect, as fishes whose
eggs increase and are finally developed outside of them. The reason is
that they produce many young, and this is their function as it is with
plants. If then they perfected the egg in themselves they must needs
be few in number, but as it is, they have so many that each uterus
seems to be an egg, at any rate in the small fishes. For these are the
most productive, just as with the other animals and plants whose
nature is analogous to theirs, for the increase of size turns with
them to seed.

  But the eggs of birds and the quadrupedal ovipara are perfect when
produced. In order that these may be preserved they must have a hard
covering  (for their envelope is soft so long as they are increasing
in size),  and the shell is made by heat squeezing out the moisture
for the earthy material; consequently the place must be hot in which
this is to happen. But the part about the hypozoma is hot, as is shown
by that being the part which concocts the food. If then the eggs
must be within the uterus, then the uterus must be near the hypozoma
in those creatures which produce their eggs in a perfect form.
Similarly it must be low down in those which produce them imperfect,
for it is profitable that it should be so. And it is more natural
for the uterus to be low down than high up, when Nature has no other
business in hand to hinder it; for its end is low down, and where is
the end, there is the function, and the uterus itself is naturally
where the function is.

                                 9

  We find differences in the vivipara also as compared with one
another. Some produce their young alive, not only externally, but also
internally, as men, horses, dogs, and all those which have hair, and
among aquatic animals, dolphins, whales, and such cetacea.

                                10

  But the cartilaginous fish and the vipers produce their young
alive externally, but first produce eggs internally. The egg is
perfect, for so only can an animal be generated from an egg, and
nothing comes from an imperfect one. It is because they are of a
cold nature, not hot as some assert, that they do not lay their eggs
externally.

                                11

  At least they certainly produce their eggs in a soft envelope, the
reason being that they have but little heat and so their nature does
not complete the process of drying the egg-shell. Because, then,
they are cold they produce soft-shelled eggs, and because the eggs are
soft they do not produce them externally; for that would have caused
their destruction.

  The process is for the most part the same as in birds, for the egg
descends and the young is hatched from it near the vagina, where the
young is produced in those animals which are viviparous from the
beginning. Therefore in such animals the uterus is dissimilar to
that of both the vivipara and ovipara, because they participate in
both classes; for it is at once near the hypozoma and also
stretching along downwards in all the cartilaginous fishes. But the
facts about this and the other kinds of uterus must be gathered from
inspection of the drawings of dissections and from the Enquiries.
Thus, because they are oviparous, laying perfect eggs, they have the
uterus placed high, but, as being viviparous, low, participating in
both classes.

  Animals that are viviparous from the beginning all have it low,
Nature here having no other business to interfere with her, and
their production having no double character. Besides this, it is
impossible for animals to be produced alive near the hypozoma, for the
foetus must needs be heavy and move, and that region in the mother
is vital and would not be able to bear the weight and the movement.
Thirdly, parturition would be difficult because of the length of the
passage to be traversed; even as it is there is difficulty with
women if they draw up the uterus in parturition by yawning or anything
of the kind, and even when empty it causes a feeling of suffocation if
moved upwards. For if a uterus is to hold a living animal it must be
stronger than in ovipara, and therefore in all the vivipara it is
fleshy, whereas when the uterus is near the hypozoma it is membranous.
And this is clear also in the case of the animals which produce
young by the mixed method, for their eggs are high up and sideways,
but the living young are produced in the lower part of the uterus.

  So much for the reason why differences are found in the uterus of
various animals, and generally why it is low in some and high in
others near the hypozoma.

                                12

  Why is the uterus always internal, but the testes sometimes
internal, sometimes external? The reason for the uterus always being
internal is that in this is contained the egg or foetus, which needs
guarding, shelter, and maturation by concoction, while the outer
surface of the body is easily injured and cold. The testes vary in
position because they also need shelter and a covering to preserve
them and to mature the semen; for it would be impossible for them,
if chilled and stiffened, to be drawn up and discharge it.
Therefore, whenever the testes are visible, they have a cuticular
covering known as the scrotum. If the nature of the skin is opposed to
this, being too hard to be adapted for enclosing them or for being
soft like a true &#39;skin&#39;, as with the scaly integument of fish and
reptiles, then the testes must needs be internal. Therefore they are
so in dolphins and all the cetacea which have them, and in the
oviparous quadrupeds among the scaly animals. The skin of birds also
is hard so that it will not conform to the size of anything and
enclose it neatly.  (This is another reason with all these animals for
their testes being internal besides those previously mentioned as
arising necessarily from the details of copulation.)  For the same
reason they are internal in the elephant and hedgehog, for the skin of
these, too, is not well suited to keep the protective part separate.

  [The position of the uterus differs in animals viviparous within
themselves and those externally oviparous, and in the latter class
again it differs in those which have the uterus low and those which
have it near the hypozoma, as in fishes compared with birds and
oviparous quadrupeds. And it is different again in those which produce
young in both ways, being oviparous internally and viviparous
externally. For those which are viviparous both internally and
externally have the uterus placed on the abdomen, as men, cattle,
dogs, and the like, since it is expedient for the safety and growth of
the foetus that no weight should be upon the uterus.]

                                13

  The passages also are different through which the solid and liquid
excreta pass out in all the vivipara. Wherefore both males and females
in this class all have a part whereby the urine is voided, and this
serves also for the issue of the semen in males, of the offspring in
females. This passage is situated above and in front of the passage of
the solid excreta. The passage is the same as that of the solid
nutriment in all those animals that have no penis, in all the ovipara,
even those of them that have a bladder, as the tortoises. For it is
for the sake of generation, not for the evacuation of the urine,
that the passages are double; but because the semen is naturally
liquid, the liquid excretion also shares the same passage. This is
clear from the fact that all animals produce semen, but all do not
void liquid excrement. Now the spermatic passages of the male must
be fixed and must not wander, and the same applies to the uterus of
the female, and this fixing must take place at either the front or the
back of the body. To take the uterus first, it is in the front of
the body in vivipara because of the foetus, but at the loin and the
back in ovipara. All animals which are internally oviparous and
externally viviparous are in an intermediate condition because they
participate in both classes, being at once oviparous and viviparous.
For the upper part of the uterus, where the eggs are produced, is
under the hypozoma by the loin and the back, but as it advances is low
at the abdomen; for it is in that part that the animal is
viviparous. In these also the passage for solid excrement and for
copulation is the same, for none of these, as has been said already,
has a separate pudendum.

  The same applies to the passages in the male, whether they have
testes or no, as to the uterus of the ovipara. For in all of them, not
only in the ovipara, the ducts adhere to the back and the region of
the spine. For they must not wander but be settled, and that is the
character of the region of the back, which gives continuity and
stability. Now in those which have internal testes, the ducts are
fixed from the first, and they are fixed in like manner if the
testes are external; then they meet together towards the region of the
penis.

  The like applies to the ducts in the dolphins, but they have their
testes hidden under the abdominal cavity.

  We have now discussed the situation of the parts contributing to
generation, and the causes thereof.

                                14

  The bloodless animals do not agree either with the sanguinea or with
each other in the fashion of the parts contributing to generation.
There are four classes still left to deal with, first the crustacea,
secondly the cephalopoda, thirdly the insects, and fourthly the
testacea. We cannot be certain about all of them, but that most of
them copulate is plain; in what manner they unite must be stated
later.

  The crustacea copulate like the retromingent quadrupeds, fitting
their tails to one another, the one supine and the other prone. For
the flaps attached to the sides of the tail being long prevent them
from uniting with the belly against the back. The males have fine
spermatic ducts, the females a membranous uterus alongside the
intestine, cloven on each side, in which the egg is produced.

                                15

  The cephalopoda entwine together at the mouth, pushing against one
another and enfolding their arms. This attitude is necessary,
because Nature has bent backwards the end of the intestine and brought
it round near the mouth, as has been said before in the treatise on
the parts of animals. The female has a part corresponding to the
uterus, plainly to be seen in each of these animals, for it contains
an egg which is at first indivisible to the eye but afterwards
splits up into many; each of these eggs is imperfect when deposited,
as with the oviparous fishes. In the cephalopoda  (as also in the
crustacea)  the same passage serves to void the excrement and leads to
the part like a uterus, for the male discharges the seminal fluid
through this passage. And it is on the lower surface of the body,
where the mantle is open and the sea-water enters the cavity. Hence
the union of the male with the female takes place at this point, for
it is necessary, if the male discharges either semen or a part of
himself or any other force, that he should unite with her at the
uterine passage. But the insertion, in the case of the poulps, of
the arm of the male into the funnel of the female, by which arm the
fishermen say the male copulates with her, is only for the sake of
attachment, and it is not an organ useful for generation, for it is
outside the passage in the male and indeed outside the body of the
male altogether.

  Sometimes also cephalopoda unite by the male mounting on the back of
the female, but whether for generation or some other cause has not yet
been observed.

                                16

  Some insects copulate and the offspring are produced from animals of
the same name, just as with the sanguinea; such are the locusts,
cicadae, spiders, wasps, and ants. Others unite indeed and generate;
but the result is not a creature of the same kind, but only a
scolex, and these insects do not come into being from animals but from
putrefying matter, liquid or solid; such are fleas, flies, and
cantharides. Others again are neither produced from animals nor
unite with each other; such are gnats, &#39;conopes&#39;, and many similar
kinds. In most of those which unite the female is larger than the
male. The males do not appear to have spermatic passages. In most
cases the male does not insert any part into the female, but the
female from below upwards into the male; this has been observed in
many cases  (as also that the male mounts the female),  the opposite
in few cases; but observations are not yet comprehensive enough to
enable us to make a distinction of classes. And generally it is the
rule with most of the oviparous fish and oviparous quadrupeds that the
female is larger than the because this is expedient in view of the
increase of bulk in conception by reason of the eggs. In the female
the part analogous to the uterus is cleft and extends along the
intestine, as with the other animals; in this are produced the results
of conception. This is clear in locusts and all other large insects
whose nature it is to unite; most insects are too small to be observed
in this respect.

  Such is the character of the generative organs in animals which were
not spoken of before. It remains now to speak of the homogeneous parts
concerned, the seminal fluid and milk. We will take the former
first, and treat of milk afterwards.

                                17

  Some animals manifestly emit semen, as all the sanguinea, but
whether the insects and cephalopoda do so is uncertain. Therefore this
is a question to be considered, whether all males do so, or not all;
and if not all, why some do and some not; and whether the female
also contributes any semen or not; and, if not semen, whether she does
not contribute anything else either, or whether she contributes
something else which is not semen. We must also inquire what those
animals which emit semen contribute by means of it to generation,
and generally what is the nature of semen, and of the so-called
catamenia in all animals which discharge this liquid.

  Now it is thought that all animals are generated out of semen, and
that the semen comes from the parents. Wherefore it is part of the
same inquiry to ask whether both male and female produce it or only
one of them, and to ask whether it comes from the whole of the body or
not from the whole; for if the latter is true it is reasonable to
suppose that it does not come from both parents either. Accordingly,
since some say that it comes from the whole of the body, we must
investigate this question first.

  The proofs from which it can be argued that the semen comes from
each and every part of the body may be reduced to four. First, the
intensity of the pleasure of coition; for the same state of feeling is
more pleasant if multiplied, and that which affects all the parts is
multiplied as compared with that which affects only one or a few.
Secondly, the alleged fact that mutilations are inherited, for they
argue that since the parent is deficient in this part the semen does
not come from thence, and the result is that the corresponding part is
not formed in the offspring. Thirdly, the resemblances to the parents,
for the young are born like them part for part as well as in the whole
body; if then the coming of the semen from the whole body is cause
of the resemblance of the whole, so the parts would be like because it
comes from each of the parts. Fourthly, it would seem to be reasonable
to say that as there is some first thing from which the whole
arises, so it is also with each of the parts, and therefore if semen
or seed is cause of the whole so each of the parts would have a seed
peculiar to itself. And these opinions are plausibly supported by such
evidence as that children are born with a likeness to their parents,
not in congenital but also in acquired characteristics; for before
now, when the parents have had scars, the children have been born with
a mark in the form of the scar in the same place, and there was a case
at Chalcedon where the father had a brand on his arm and the letter
was marked on the child, only confused and not clearly articulated.
That is pretty much the evidence on which some believe that the
semen comes from all the body.

                                18

  On examining the question, however, the opposite appears more
likely, for it is not hard to refute the above arguments and the
view involves impossibilities. First, then, the resemblance of
children to parents is no proof that the semen comes from the whole
body, because the resemblance is found also in voice, nails, hair, and
way of moving, from which nothing comes. And men generate before
they yet have certain characters, such as a beard or grey hair.
Further, children are like their more remote ancestors from whom
nothing has come, for the resemblances recur at an interval of many
generations, as in the case of the woman in Elis who had intercourse
with the Aethiop; her daughter was not an Aethiop but the son of
that daughter was. The same thing applies also to plants, for it is
clear that if this theory were true the seed would come from all parts
of plants also; but often a plant does not possess one part, and
another part may be removed, and a third grows afterwards. Besides,
the seed does not come from the pericarp, and yet this also comes into
being with the same form as in the parent plant.

  We may also ask whether the semen comes from each of the homogeneous
parts only, such as flesh and bone and sinew, or also from the
heterogeneous, such as face and hands. For if from the former only, we
object that resemblance exists rather in the heterogeneous parts, such
as face and hands and feet; if then it is not because of the semen
coming from all parts that children resemble their parents in these,
what is there to stop the homogeneous parts also from being like for
some other reason than this? If the semen comes from the heterogeneous
alone, then it does not come from all parts; but it is more fitting
that it should come from the homogeneous parts, for they are prior
to the heterogeneous which are composed of them; and as children are
born like their parents in face and hands, so they are, necessarily,
in flesh and nails. If the semen comes from both, what would be the
manner of generation? For the heteroeneous parts are composed of the
homogneous, so that to come from the former would be to come from
the latter and from their composition. To make this clearer by an
illustration, take a written name; if anything came from the whole
of it, it would be from each of the syllables, and if from these, from
the letters and their composition. So that if really flesh and bones
are composed of fire and the like elements, the semen would come
rather from the elements than anything else, for how can it come
from their composition? Yet without this composition there would be no
resemblance. If again something creates this composition later, it
would be this that would be the cause of the resemblance, not the
coming of the semen from every part of the body.

  Further, if the parts of the future animal are separated in the
semen, how do they live? and if they are connected, they would form
a small animal.

  And what about the generative parts? For that which comes from the
male is not similar to what comes from the female.

  Again, if the semen comes from all parts of both parents alike,
the result is two animals, for the offspring will have all the parts
of both. Wherefore Empedocles seems to say what agrees pretty well
with this view  (if we are to adopt it),  to a certain extent at any
rate, but to be wrong if we think otherwise. What he says agrees
with it when he declares that there is a sort of tally in the male and
female, and that the whole offspring does not come from either, &#39;but
sundered is the fashion of limbs, some in man&#39;s...&#39; For why does not
the female generate from herself if the semen comes from all parts
alike and she has a receptacle ready in the uterus? But, it seems,
either it does not come from all the parts, or if it does it is in the
way Empedocles says, not the same parts coming from each parent, which
is why they need intercourse with each other.

  Yet this also is impossible, just as much as it is impossible for
the parts when full grown to survive and have life in them when torn
apart, as Empedocles accounts for the creation of animals; in the time
of his &#39;Reign of Love&#39;, says he, &#39;many heads sprang up without necks,&#39;
and later on these isolated parts combined into animals. Now that this
is impossible is plain, for neither would the separate parts be able
to survive without having any soul or life in them, nor if they were
living things, so to say, could several of them combine so as to
become one animal again. Yet those who say that semen comes from the
whole of the body really have to talk in that way, and as it
happened then in the earth during the &#39;Reign of Love&#39;, so it happens
according to them in the body. Now it is impossible that the parts
should be united together when they come into being and should come
from different parts of the parent, meeting together in one place.
Then how can the upper and lower, right and left, front and back parts
have been &#39;sundered&#39;? All these points are unintelligible. Further,
some parts are distinguished by possessing a faculty, others by
being in certain states or conditions; the heterogeneous, as tongue
and hand, by the faculty of doing something, the homogeneous by
hardness and softness and the other similar states. Blood, then,
will not be blood, nor flesh flesh, in any and every state. It is
clear, then, that that which comes from any part, as blood from
blood or flesh from flesh, will not be identical with that part. But
if it is something different from which the blood of the offspring
comes, the coming of the semen from all the parts will not be the
cause of the resemblance, as is held by the supporters of this theory.
For if blood is formed from something which is not blood, it is enough
that the semen come from one part only, for why should not all the
other parts of the offspring as well as blood be formed from one
part of the parent? Indeed, this theory seems to be the same as that
of Anaxagoras, that none of the homogeneous parts come into being,
except that these theorists assume, in the case of the generation of
animals, what he assumed of the universe.

  Then, again, how will these parts that came from all the body of the
parent be increased or grow? It is true that Anaxagoras plausibly says
that particles of flesh out of the food are added to the flesh. But if
we do not say this  (while saying that semen comes from all parts of
the body),  how will the foetus become greater by the addition of
something else if that which is added remain unchanged? But if that
which is added can change, then why not say that the semen from the
very first is of such a kind that blood and flesh can be made out of
it, instead of saying that it itself is blood and flesh? Nor is
there any other alternative, for surely we cannot say that it is
increased later by a process of mixing, as wine when water is poured
into it. For in that case each element of the mixture would be
itself at first while still unmixed, but the fact rather is that flesh
and bone and each of the other parts is such later. And to say that
some part of the semen is sinew and bone is quite above us, as the
saying is.

  Besides all this there is a difficulty if the sex is determined in
conception  (as Empedocles says: &#39;it is shed in clean vessels; some
wax female, if they fall in with cold&#39;).  Anyhow, it is plain that
both men and women change not only from infertile to fertile, but also
from bearing female to bearing male offspring, which looks as if the
cause does not lie in the semen coming from all the parent or not, but
in the mutual proportion or disproportion of that comes from the woman
and the man, or in something of this kind. It is clear, then, if we
are to put this down as being so, that the female sex is not
determined by the semen coming from any particular part, and
consequently neither is the special sexual part so determined  (if
really the same semen can become either male or female child, which
shows that the sexual part does not exist in the semen).  Why, then,
should we assert this of this part any more than of others? For if
semen does not come from this part, the uterus, the same account may
be given of the others.

  Again, some creatures come into being neither from parents of the
same kind nor from parents of a different kind, as flies and the
various kinds of what are called fleas; from these are produced
animals indeed, but not in this case of similar nature but a kind of
scolex. It is plain in this case that the young of a different kind
are not produced by semen coming from all parts of the parent, for
they would then resemble them, if indeed resemblance is a sign of
its coming from all parts.

  Further even among animals some produce many young from a single
coition  (and something like this is universal among plants, for it is
plain that they bear all the fruit of a whole season from a single
movement).  And yet how would this be possible if the semen were
secreted from all the body? For from a single coition and a single
segregation of the semen scattered throughout the body must needs
follow only a single secretion. Nor is it possible for it to be
separated in the uterus, for this would no longer be a mere separation
of semen, but, as it were, a severance from a new plant or animal.

  Again, the cuttings from a plant bear seed; clearly, therefore, even
before they were cut from the parent plant, they bore their fruit from
their own mass alone, and the seed did not come from all the plant.

  But the greatest proof of all is derived from observations we have
sufficiently established on insects. For, if not in all, at least in
most of these, the female in the act of copulation inserts a part of
herself into the male. This, as we said before, is the way they
copulate, for the females manifestly insert this from below into the
males above, not in all cases, but in most of those observed. Hence it
seems clear that, when the males do emit semen, then also the cause of
the generation is not its coming from all the body, but something else
which must be investigated hereafter. For even if it were true that it
comes from all the body, as they say, they ought not to claim that
it comes from all parts of it, but only from the creative part- from
the workman, so to say, not the material he works in. Instead of that,
they talk as if one were to say that the semen comes from the shoes,
for, generally speaking, if a son is like his father, the shoes he
wears are like his father&#39;s shoes.

  As to the vehemence of pleasure in sexual intercourse, it is not
because the semen comes from all the body, but because there is a
strong friction  (wherefore if this intercourse is often repeated
the pleasure is diminished in the persons concerned).  Moreover, the
pleasure is at the end of the act, but it ought, on the theory, to
be in each of the parts, and not at the same time, but sooner in
some and later in others.

  If mutilated young are born of mutilated parents, it is for the same
reason as that for which they are like them. And the young of
mutilated parents are not always mutilated, just as they are not
always like their parents; the cause of this must be inquired into
later, for this problem is the same as that.

  Again, if the female does not produce semen, it is reasonable to
suppose it does not come from all the body of the male either.
Conversely, if it does not come from all the male it is not
unreasonable to suppose that it does not come from the female, but
that the female is cause of the generation in some other way. Into
this we must next inquire, since it is plain that the semen is not
secreted from all the parts.

  In this investigation and those which follow from it, the first
thing to do is to understand what semen is, for then it will be easier
to inquire into its operations and the phenomena connected with it.
Now the object of semen is to be of such a nature that from it as
their origin come into being those things which are naturally
formed, not because there is any agent which makes them from it as
simply because this is the semen. Now we speak of one thing coming
from another in many senses; it is one thing when we say that night
comes from day or a man becomes man from boy, meaning that A follows
B; it is another if we say that a statue is made from bronze and a bed
from wood, and so on in all the other cases where we say that the
thing made is made from a material, meaning that the whole is formed
from something preexisting which is only put into shape. In a third
sense a man becomes unmusical from being musical, sick from being
well, and generally in this sense contraries arise from contraries.
Fourthly, as in the &#39;climax&#39; of Epicharmus; thus from slander comes
railing and from this fighting, and all these are from something in
the sense that it is the efficient cause. In this last class sometimes
the efficient cause is in the things themselves, as in the last
mentioned  (for the slander is a part of the whole trouble),  and
sometimes external, as the art is external to the work of art or the
torch to the burning house. Now the offspring comes from the semen,
and it is plainly in one of the two following senses that it does
so- either the semen is the material from which it is made, or it is
the first efficient cause. For assuredly it is not in the sense of A
being after B, as the voyage comes from, i.e. after, the
Panathenaea; nor yet as contraries come from contraries, for then
one of the two contraries ceases to be, and a third substance must
exist as an immediate underlying basis from which the new thing
comes into being. We must discover then, in which of the two other
classes the semen is to be put, whether it is to be regarded as
matter, and therefore acted upon by something else, or as a form,
and therefore acting upon something else, or as both at once. For
perhaps at the same time we shall see clearly also how all the
products of semen come into being from contraries, since coming into
being from contraries is also a natural process, for some animals do
so, i.e. from male and female, others from only one parent, as is
the case with plants and all those animals in which male and female
are not separately differentiated. Now that which comes from the
generating parent is called the seminal fluid, being that which
first has in it a principle of generation, in the case of all
animals whose nature it is to unite; semen is that which has in it the
principles from both united parents, as the first mixture which arises
from the union of male and female, be it a foetus or an ovum, for
these already have in them that which comes from both.  (Semen, or
seed, and grain differ only in the one being earlier and the other
later, grain in that it comes from something else, i.e. the seed,
and seed in that something else, the grain, comes from it, for both
are really the same thing.)

  We must again take up the question what the primary nature of what
is called semen is. Needs must everything which we find in the body
either be (1) one of the natural parts, whether homogeneous or
heterogeneous, or (2) an unnatural part such as a growth, or (3) a
secretion or excretion, or (4) waste-product, or (5) nutriment.  (By
secretion or excretion I mean the residue of the nutriment, by
waste-product that which is given off from the tissues by an unnatural
decomposition.)

  Now that semen cannot be a part of the body is plain, for it is
homogeneous, and from the homogeneous nothing is composed, e.g. from
only sinew or only flesh; nor is it separated as are all the other
parts. But neither is it contrary to Nature nor a defect, for it
exists in all alike, and the development of the young animal comes
from it. Nutriment, again, is obviously introduced from without.

  It remains, then, that it must be either a waste-product or a
secretion or excretion. Now the ancients seem to think that it is a
waste-product, for when they say that it comes from all the body by
reason of the heat of the movement of the body in copulation, they
imply that it is a kind of waste-product. But these are contrary to
Nature, and from such arises nothing according to Nature. So then it
must be a secretion or excretion.

  But, to go further into it, every secretion or excretion is either
of useless or useful nutriment; by &#39;useless&#39; I mean that from which
nothing further is contributed to natural growth, but which is
particularly mischievous to the body if too much of it is consumed; by
&#39;useful&#39; I mean the opposite. Now it is evident that it cannot be of
the former character, for such is most abundant in persons of the
worst condition of body through age or sickness; semen, on the
contrary, is least abundant in them for either they have none at all
or it is not fertile, because a useless and morbid secretion is
mingled with it.

  Semen, then, is part of a useful secretion. But the most useful is
the last and that from which finally is formed each of the parts of
the body. For secretions are either earlier or later; of the nutriment
in the first stage the secretion is phlegm and the like, for phlegm
also is a secretion of the useful nutriment, an indication of this
being that if it is mixed with pure nutriment it is nourishing, and
that it is used up in cases of illness. The final secretion is the
smallest in proportion to the quantity of nutriment. But we must
reflect that the daily nutriment by which animals and plants grow is
but small, for if a very little be added continually to the same thing
the size of it will become excessive.

  So we must say the opposite of what the ancients said. For whereas
they said that semen is that which comes from all the body, we shall
say it is that whose nature is to go to all of it, and what they
thought a waste-product seems rather to be a secretion. For it is more
reasonable to suppose that the last extract of the nutriment which
goes to all parts resembles that which is left over from it, just as
part of a painter&#39;s colour is often left over resembling that which he
has used up. Waste-products, on the contrary, are always due to
corruption or decay and to a departure from Nature.

  A further proof that it is not a waste-product, but rather a
secretion, is the fact that the large animals have few young, the
small many. For the large must have more waste and less secretion,
since the great size of the body causes most of the nutriment to be
used up, so that the residue or secretion is small.

  Again, no place has been set apart by Nature for waste-products
but they flow wherever they can find an easy passage in the body,
but a place has been set apart for all the natural secretions; thus
the lower intestine serves for the excretion of the solid nutriment,
the bladder for that of the liquid; for the useful part of the
nutriment we have the upper intestine, for the spermatic secretions
the uterus and pudenda and breasts, for it is collected and flows
together into them.

  And the resulting phenomena are evidence that semen is what we
have said, and these result because such is the nature of the
secretion. For the exhaustion consequent on the loss of even a very
little of the semen is conspicuous because the body is deprived of the
ultimate gain drawn from the nutriment. With some few persons, it is
true, during a short time in the flower of their youth the loss of it,
if it be excessive in quantity, is an alleviation  (just as in the
case of the nutriment in its first stage, if too much have been taken,
since getting rid of this also makes the body more comfortable),
and so it may be also when other secretions come away with it, for
in that case it is not only semen that is lost but also other
influences come away mingled with it, and these are morbid. Wherefore,
with some men at least, that which comes from them proves sometimes
incapable of procreation because the seminal element in it is so
small. But still in most men and as a general rule the result of
intercourse is exhaustion and weakness rather than relief, for the
reason given. Moreover, semen does not exist in them either in
childhood or in old age or in sickness- in the last case because of
weakness, in old age because they do not sufficiently concoct their
food, and in childhood because they are growing and so all the
nutriment is used up too soon, for in about five years, in the case of
human beings at any rate, the body seems to gain half the height
that is gained in all the rest of life.

  In many animals and plants we find a difference in this connexion
not only between kinds as compared with kinds, but also between
similar individuals of the same kind as compared with each other, e.g.
man with man or vine with vine. Some have much semen, others little,
others again none at all, not through weakness but the contrary, at
any rate in some cases. This is because the nutriment is used up to
form the body, as with some human beings, who, being in good condition
and developing much flesh or getting rather too fat, produce less
semen and are less desirous of intercourse. Like this is what
happens with those vines which &#39;play the goat&#39;, that is, luxuriate
wantonly through too much nutrition, for he-goats when fat are less
inclined to mount the female; for which reason they thin them before
breeding from them, and say that the vines &#39;play the goat&#39;, so calling
it from the condition of the goats. And fat people, women as well as
men, appear to be less fertile than others from the fact that the
secretion when in process of concoction turns to fat with those who
are too well-nourished. For fat also is a healthy secretion due to
good living.

  In some cases no semen is produced at all, as by the willow and
poplar. This condition is due to each of the two causes, weakness
and strength; the former prevents concoction of the nutriment, the
latter causes it to be all consumed, as said above. In like manner
other animals produce much semen through weakness as well as through
strength, when a great quantity of a useless secretion is mixed with
it; this sometimes results in actual disease when a passage is not
found to carry off the impurity, and though some recover of this,
others actually die of it. For corrupt humours collect here as in
the urine, which also has been known to cause disease.

  [Further the same passage serves for urine and semen; and whatever
animals have both kinds of excrement, that of liquid and that of solid
nutriment, discharge the semen by the same passage as the liquid
excrement  (for it is a secretion of a liquid, since the nutriment
of all animals is rather liquid than solid),  but those which have
no liquid excrement discharge it at the passage of the solid
residua. Moreover, waste-products are always morbid, but the removal
of the secretion is useful; now the discharge of the semen
participates in both characteristics because it takes up some of the
non-useful nutriment. But if it were a waste-product it would be
always harmful; as it is, it is not so.]

  From what has been said, it is clear that semen is a secretion of
useful nutriment, and that in its last stage, whether it is produced
by all or no.

                                19

  After this we must distinguish of what sort of nutriment it is a
secretion, and must discuss the catamenia which occur in certain of
the vivipara. For thus we shall make it clear (1) whether the female
also produces semen like the male and the foetus is a single mixture
of two semens, or whether no semen is secreted by the female, and, (2)
if not, whether she contributes nothing else either to generation
but only provides a receptacle, or whether she does contribute
something, and, if so, how and in what manner she does so.

  We have previously stated that the final nutriment is the blood in
the sanguinea and the analogous fluid in the other animals. Since
the semen is also a secretion of the nutriment, and that in its
final stage, it follows that it will be either (1) blood or that which
is analogous to blood, or (2) something formed from this. But since it
is from the blood, when concocted and somehow divided up, that each
part of the body is made, and since the semen if properly concocted is
quite of a different character from the blood when it is separated
from it, but if not properly concocted has been known in some cases to
issue in a bloody condition if one forces oneself too often to
coition, therefore it is plain that semen will be a secretion of the
nutriment when reduced to blood, being that which is finally
distributed to the parts of the body. And this is the reason why it
has so great power, for the loss of the pure and healthy blood is an
exhausting thing; for this reason also it is natural that the
offspring should resemble the parents, for that which goes to all
the parts of the body resembles that which is left over. So that the
semen which is to form the hand or the face or the whole animal is
already the hand or face or whole animal undifferentiated, and what
each of them is actually such is the semen potentially, either in
virtue of its own mass or because it has a certain power in itself.
I mention these alternatives here because we have not yet made it
clear from the distinctions drawn hitherto whether it is the matter of
the semen that is the cause of generation, or whether it has in it
some faculty and efficient cause thereof, for the hand also or any
other bodily part is not hand or other part in a true sense if it be
without soul or some other power, but is only called by the same
name as the living hand.

  On this subject, then, so much may be laid down. But since it is
necessary (1) that the weaker animal also should have a secretion
greater in quantity and less concocted, and (2) that being of such a
nature it should be a mass of sanguineous liquid, and (3) since that
which Nature endows with a smaller portion of heat is weaker, and
(4) since it has already been stated that such is the character of the
female- putting all these considerations together we see that the
sanguineous matter discharged by the female is also a secretion. And
such is the discharge of the so-called catamenia.

  It is plain, then, that the catamenia are a secretion, and that they
are analogous in females to the semen in males. The circumstances
connected with them are evidence that this view is correct. For the
semen begins to appear in males and to be emitted at the same time
of life that the catamenia begin to flow in females, and that they
change their voice and their breasts begin to develop. So, too, in the
decline of life the generative power fails in the one sex and the
catamenia in the other.

  The following signs also indicate that this discharge in females
is a secretion. Generally speaking women suffer neither from
haemorrhoids nor bleeding at the nose nor anything else of the sort
except when the catamenia are ceasing, and if anything of the kind
occurs the flow is interfered with because the discharge is diverted
to it.

  Further, the blood-vessels of women stand out less than those of
men, and women are rounder and smoother because the secretion which in
men goes to these vessels is drained away with the catamenia. We
must suppose, too, that the same cause accounts for the fact that
the bulk of the body is smaller in females than in males among the
vivipara, since this is the only class in which the catamenia are
discharged from the body. And in this class the fact is clearest in
women, for the discharge is greater in women than in the other
animals. Wherefore her pallor and the absence of prominent
blood-vessels is most conspicuous, and the deficient development of
her body compared with a man&#39;s is obvious.

  Now since this is what corresponds in the female to the semen in the
male, and since it is not possible that two such discharges should
be found together, it is plain that the female does not contribute
semen to the generation of the offspring. For if she had semen she
would not have the catamenia; but, as it is, because she has the
latter she has not the former.

  It has been stated then that the catamenia are a secretion as the
semen is, and confirmation of this view may be drawn from some of
the phenomena of animals. For fat creatures produce less semen than
lean ones, as observed before. The reason is that fat also, like
semen, is a secretion, is in fact concocted blood, only not
concocted in the same way as the semen. Thus, if the secretion is
consumed to form fat the semen is naturally deficient. And so among
the bloodless animals the cephalopoda and crustacea are in best
condition about the time of producing eggs, for, because they are
bloodless and no fat is formed in them, that which is analogous in
them to fat is at that season drawn off to form the spermatic
secretion.

  And a proof that the female does not emit similar semen to the male,
and that the offspring is not formed by a mixture of both, as some
say, is that often the female conceives without the sensation of
pleasure in intercourse, and if again the pleasure is experience by
her no less than by the male and the two sexes reach their goal
together, yet often no conception takes place unless the liquid of the
so-called catamenia is present in a right proportion. Hence the female
does not produce young if the catamenia are absent altogether, nor
often when, they being present, the efflux still continues; but she
does so after the purgation. For in the one case she has not the
nutriment or material from which the foetus can be framed by the power
coming from the male and inherent in the semen, and in the other it is
washed away with the catamenia because of their abundance. But when
after their occurrence the greater part has been evacuated, the
remainder is formed into a foetus. Cases of conception when the
catamenia do not occur at all, or of conception during their discharge
instead of after it, are due to the fact that in the former instance
there is only so much liquid to begin with as remains behind after the
discharge in fertile women, and no greater quantity is secreted so
as to come away from the body, while in the latter instance the
mouth of the uterus closes after the discharge. When, therefore, the
quantity already expelled from the body is great but the discharge
still continues, only not on such a scale as to wash away the semen,
then it is that conception accompanies coition. Nor is it at all
strange that the catamenia should still continue after conception
(for even after it they recur to some extent, but are scanty and do
not last during all the period of gestation; this, however, is a
morbid phenomenon, wherefore it is found only in a few cases and
then seldom, whereas it is that which happens as a regular thing
that is according to Nature).

  It is clear then that the female contributes the material for
generation, and that this is in the substance of the catamenia, and
that they are a secretion.

                                20

  Some think that the female contributes semen in coition because
the pleasure she experiences is sometimes similar to that of the male,
and also is attended by a liquid discharge. But this discharge is
not seminal; it is merely proper to the part concerned in each case,
for there is a discharge from the uterus which occurs in some women
but not in others. It is found in those who are fair-skinned and of
a feminine type generally, but not in those who are dark and of a
masculine appearance. The amount of this discharge, when it occurs, is
sometimes on a different scale from the emission of semen and far
exceeds it. Moreover, different kinds of food cause a great difference
in the quantity of such discharges; for instance some
pungently-flavoured foods cause them to be conspicuously increased.
And as to the pleasure which accompanies coition it is due to emission
not only of semen, but also of a spiritus, the coming together of
which precedes the emission. This is plain in the case of boys who are
not yet able to emit semen, but are near the proper age, and of men
who are impotent, for all these are capable of pleasure by
attrition. And those who have been injured in the generative organs
sometimes suffer from diarrhoea because the secretion, which they
are not able to concoct and turn into semen, is diverted into the
intestine. Now a boy is like a woman in form, and the woman is as it
were an impotent male, for it is through a certain incapacity that the
female is female, being incapable of concocting the nutriment in its
last stage into semen  (and this is either blood or that which is
analogous to it in animals which are bloodless owing to the coldness
of their nature).  As then diarrhoea is caused in the bowels by the
insufficient concoction of the blood, so are caused in the
blood-vessels all discharges of blood, including that of the
catamenia, for this also is such a discharge, only it is natural
whereas the others are morbid.

  Thus it is clear that it is reasonable to suppose that generation
comes from this. For the catamenia are semen not in a pure state but
in need of working up, as in the formation of fruits the nutriment
is present, when it is not yet sifted thoroughly, but needs working up
to purify it. Thus the catamenia cause generation mixture with the
semen, as this impure nutriment in plants is nutritious when mixed
with pure nutriment.

  And a sign that the female does not emit semen is the fact that
the pleasure of intercourse is caused by touch in the same region of
the female as of the male; and yet is it not from thence that this
flow proceeds. Further, it is not all females that have it at all, but
only the sanguinea, and not all even of these, but only those whose
uterus is not near the hypozoma and which do not lay eggs; it is not
found in the animals which have no blood but only the analogous fluid
(for what is blood in the former is represented by another fluid in
the latter).  The reason why neither the latter nor those sanguinea
mentioned  (i.e. those whose uterus is low and which do not lay eggs)
have this effluxion is the dryness of their bodies; this allows but
little matter to be secreted, only enough for generation but not
enough to be discharged from the body. All animals that are viviparous
without producing eggs first  (such are man and all quadrupeds which
bend their hind-legs outwards, for all these are viviparous without
producing eggs)- all these have the catamenia, unless they are
defective in development as the mule, only the efflux is not
abundant as in women. Details of the facts in each animal have been
given in the Enquiries concerning animals.

  The catamenia are more abundant in women than in the other
animals, and men emit the most semen in proportion to their size.
The reason is that the composition of their bodies is liquid and hot
compared to others, for more matter must be secreted in such a case.
Further, man has no such parts in his body as those to which the
superfluous matter is diverted in the other animals; for he has no
great quantity of hair in proportion to his body, nor outgrowths of
bones, horns, and teeth.

  There is evidence that the semen is in the catamenia, for, as said
before, this secretion appears in the male at the same time of life as
the catamenia in the female; this indicates that the parts destined to
receive each of these secretions are differentiated at the same time
in both sexes; and as the neighboring parts in both become swollen the
hair of puberty springs forth in both alike. As the parts in
question are on the point of differentiating they are distended by the
spiritus; this is clearer in males in the testes, but appears also
about the breasts; in females it is more marked in the breasts, for it
is when they have risen two fingers&#39; breadth that the catamenia
generally begin.

  Now, in all living things in which the male and female are not
separated the semen  (or seed)  is a sort of embryo; by embryo I
mean the first mixture of male and female; hence, from one semen comes
one bodys- for example, one stalk of wheat from one grain, as one
animal from one egg  (for twin eggs are really two eggs).  But in
whatever kinds the sexes are distinguished, in these many animals
may come from one emission of semen, showing that the semen differs in
its nature in plants and animals. A proof of this is that animals
which can bear more than one young one at a time do so in
consequence of only one coition. Whereby, too, it is plain that the
semen does not come from the whole of the body; for neither would
the different parts of the semen already be separated as soon as
discharged from the same part, nor could they be separated in the
uterus if they had once entered it all together; but what does
happen is just what one would expect, since what the male
contributes to generation is the form and the efficient cause, while
the female contributes the material. In fact, as in the coagulation of
milk, the milk being the material, the fig-juice or rennet is that
which contains the curdling principle, so acts the secretion of the
male, being divided into parts in the female. Why it is sometimes
divided into more or fewer parts, and sometimes not divided at all,
will be the subject of another discussion. But because it does not
differ in kind at any rate this does not matter, but what does
matter is only that each part should correspond to the material, being
neither too little to concoct it and fix it into form, nor too much so
as to dry it up; it then generates a number of offspring. But from
this first formative semen, if it remains one, and is not divided,
only one young one comes into being.

  That, then, the female does not contribute semen to generation,
but does contribute something, and that this is the matter of the
catamenia, or that which is analogous to it in bloodless animals, is
clear from what has been said, and also from a general and abstract
survey of the question. For there must needs be that which generates
and that from which it generates; even if these be one, still they
must be distinct in form and their essence must be different; and in
those animals that have these powers separate in two sexes the body
and nature of the active and the passive sex must also differ. If,
then, the male stands for the effective and active, and the female,
considered as female, for the passive, it follows that what the female
would contribute to the semen of the male would not be semen but
material for the semen to work upon. This is just what we find to be
the case, for the catamenia have in their nature an affinity to the
primitive matter.

                                21

  So much for the discussion of this question. At the same time the
answer to the next question we have to investigate is clear from these
considerations, I mean how it is that the male contributes to
generation and how it is that the semen from the male is the cause
of the offspring. Does it exist in the body of the embryo as a part of
it from the first, mingling with the material which comes from the
female? Or does the semen communicate nothing to the material body
of the embryo but only to the power and movement in it? For this power
is that which acts and makes, while that which is made and receives
the form is the residue of the secretion in the female. Now the latter
alternative appears to be the right one both a priori and in view of
the facts. For, if we consider the question on general grounds, we
find that, whenever one thing is made from two of which one is
active and the other passive, the active agent does not exist in
that which is made; and, still more generally, the same applies when
one thing moves and another is moved; the moving thing does not
exist in that which is moved. But the female, as female, is passive,
and the male, as male, is active, and the principle of the movement
comes from him. Therefore, if we take the highest genera under which
they each fall, the one being active and motive and the other
passive and moved, that one thing which is produced comes from them
only in the sense in which a bed comes into being from the carpenter
and the wood, or in which a ball comes into being from the wax and the
form. It is plain then that it is not necessary that anything at all
should come away from the male, and if anything does come away it does
not follow that this gives rise to the embryo as being in the
embryo, but only as that which imparts the motion and as the form;
so the medical art cures the patient.

  This a priori argument is confirmed by the facts. For it is for this
reason that some males which unite with the female do not, it appears,
insert any part of themselves into the female, but on the contrary the
female inserts a part of herself into the male; this occurs in some
insects. For the effect produced by the semen in the female  (in the
case of those animals whose males do insert a part)  is produced in
the case of these insects by the heat and power in the male animal
itself when the female inserts that part of herself which receives the
secretion. And therefore such animals remain united a long time, and
when they are separated the young are produced quickly. For the
union lasts until that which is analogous to the semen has done its
work, and when they separate the female produces the embryo quickly;
for the young is imperfect inasmuch as all such creatures give birth
to scoleces.

  What occurs in birds and oviparous fishes is the greatest proof that
neither does the semen come from all parts of the male nor does he
emit anything of such a nature as to exist within that which is
generated, as part of the material embryo, but that he only makes a
living creature by the power which resides in the semen  (as we said
in the case of those insects whose females insert a part of themselves
into the male).  For if a hen-bird is in process of producing
wind-eggs and is then trodden by the cock before the egg has begun
to whiten and while it is all still yellow, then they become fertile
instead of being wind-eggs. And if while it is still yellow she be
trodden by another cock, the whole brood of chicks turn out like the
second cock. Hence some of those who are anxious to rear fine birds
act thus; they change the cocks for the first and second treading, not
as if they thought that the semen is mingled with the egg or exists in
it, or that it comes from all parts of the cock; for if it did it
would have come from both cocks, so that the chick would have all
its parts doubled. But it is by its force that the semen of the male
gives a certain quality to the material and the nutriment in the
female, for the second semen added to the first can produce this
effect by heat and concoction, as the egg acquires nutriment so long
as it is growing.

  The same conclusion is to be drawn from the generation of
oviparous fishes. When the female has laid her eggs, the male spinkles
the milt over them, and those eggs are fertilized which it reaches,
but not the others; this shows that the male does not contribute
anything to the quantity but only to the quality of the embryo.

  From what has been said it is plain that the semen does not come
from the whole of the body of the male in those animals which emit it,
and that the contribution of the female to the generative product is
not the same as that of the male, but the male contributes the
principle of movement and the female the material. This is why the
female does not produce offspring by herself, for she needs a
principle, i.e. something to begin the movement in the embryo and to
define the form it is to assume. Yet in some animals, as birds, the
nature of the female unassisted can generate to a certain extent,
for they do form something, only it is incomplete; I mean the
so-called wind-eggs.

                                22

  For the same reason the development of the embryo takes place in the
female; neither the male himself nor the female emits semen into the
male, but the female receives within herself the share contributed
by both, because in the female is the material from which is made
the resulting product. Not only must the mass of material exist
there from which the embryo is formed in the first instance, but
further material must constantly be added that it may increase in
size. Therefore the birth must take place in the female. For the
carpenter must keep in close connexion with his timber and the
potter with his clay, and generally all workmanship and the ultimate
movement imparted to matter must be connected with the material
concerned, as, for instance, architecture is in the buildings it
makes.

  From these considerations we may also gather how it is that the male
contributes to generation. The male does not emit semen at all in some
animals, and where he does this is no part of the resulting embryo;
just so no material part comes from the carpenter to the material,
i.e. the wood in which he works, nor does any part of the
carpenter&#39;s art exist within what he makes, but the shape and the form
are imparted from him to the material by means of the motion he sets
up. It is his hands that move his tools, his tools that move the
material; it is his knowledge of his art, and his soul, in which is
the form, that moves his hands or any other part of him with a
motion of some definite kind, a motion varying with the varying nature
of the object made. In like manner, in the male of those animals which
emit semen Nature uses the semen as a tool and as possessing motion in
actuality, just as tools are used in the products of any art, for in
them lies in a certain sense the motion of the art. Such, then, is the
way in which these males contribute to generation. But when the male
does not emit semen, but the female inserts some part of herself
into the male, this is parallel to a case in which a man should
carry the material to the workman. For by reason of weakness in such
males Nature is not able to do anything by any secondary means, but
the movements imparted to the material are scarcely strong enough when
Nature herself watches over them. Thus here she resembles a modeller
in clay rather than a carpenter, for she does not touch the work she
is forming by means of tools, but, as it were, with her own hands.

                                23

  In all animals which can move about, the sexes are separated, one
individual being male and one female, though both are the same in
species, as with man and horse. But in plants these powers are
mingled, female not being separated from male. Wherefore they generate
out of themselves, and do not emit semen but produce an embryo, what
is called the seed. Empedocles puts this well in the line: &#39;and thus
the tall trees oviposit; first olives...&#39; For as the egg is an embryo,
a certain part of it giving rise to the animal and the rest being
nutriment, so also from a part of the seed springs the growing
plant, and the rest is nutriment for the shoot and the first root.

  In a certain sense the same thing happens also in those animals
which have the sexes separate. For when there is need for them to
generate the sexes are no longer separated any more than in plants,
their nature desiring that they shall become one; and this is plain to
view when they copulate and are united, that one animal is made out of
both.

  It is the nature of those creatures which do not emit semen to
remain united a long time until the male element has formed the
embryo, as with those insects which copulate. The others so remain
only until the male has discharged from the parts of himself
introduced something which will form the embryo in a longer time, as
among the sanguinea. For the former remain paired some part of a
day, while the semen forms the embryo in several days. And after
emitting this they cease their union.

  And animals seem literally to be like divided plants, as though
one should separate and divide them, when they bear seed, into the
male and female existing in them.

  In all this Nature acts like an intelligent workman. For to the
essence of plants belongs no other function or business than the
production of seed; since, then, this is brought about by the union of
male and female, Nature has mixed these and set them together in
plants, so that the sexes are not divided in them. Plants, however,
have been investigated elsewhere. But the function of the animal is
not only to generate  (which is common to all living things),  but
they all of them participate also in a kind of knowledge, some more
and some less, and some very little indeed. For they have
sense-perception, and this is a kind of knowledge.  (If we consider
the value of this we find that it is of great importance compared with
the class of lifeless objects, but of little compared with the use
of the intellect. For against the latter the mere participation in
touch and taste seems to be practically nothing, but beside absolute
insensibility it seems most excellent; for it would seem a treasure to
gain even this kind of knowledge rather than to lie in a state of
death and non-existence.)  Now it is by sense-perception that an
animal differs from those organisms which have only life. But since,
if it is a living animal, it must also live; therefore, when it is
necessary for it to accomplish the function of that which has life, it
unites and copulates, becoming like a plant, as we said before.

  Testaceous animals, being intermediate between animals and plants,
perform the function of neither class as belonging to both. As
plants they have no sexes, and one does not generate in another; as
animals they do not bear fruit from themselves like plants; but they
are formed and generated from a liquid and earthy concretion. However,
we must speak later of the generation of these animals.

                              Book II

                                 1

  THAT the male and the female are the principles of generation has
been previously stated, as also what is their power and their essence.
But why is it that one thing becomes and is male, another female? It
is the business of our discussion as it proceeds to try and point
out (1) that the sexes arise from Necessity and the first efficient
cause, (2) from what sort of material they are formed. That (3) they
exist because it is better and on account of the final cause, takes us
back to a principle still further remote.

  Now (1) some existing things are eternal and divine whilst others
admit of both existence and non-existence. But (2) that which is noble
and divine is always, in virtue of its own nature, the cause of the
better in such things as admit of being better or worse, and what is
not eternal does admit of existence and non-existence, and can partake
in the better and the worse. And (3) soul is better than body, and
living, having soul, is thereby better than the lifeless which has
none, and being is better than not being, living than not living.
These, then, are the reasons of the generation of animals. For since
it is impossible that such a class of things as animals should be of
an eternal nature, therefore that which comes into being is eternal in
the only way possible. Now it is impossible for it to be eternal as an
individual  (though of course the real essence of things is in the
individual)- were it such it would be eternal- but it is possible
for it as a species. This is why there is always a class of men and
animals and plants. But since the male and female essences are the
first principles of these, they will exist in the existing individuals
for the sake of generation. Again, as the first efficient or moving
cause, to which belong the definition and the form, is better and more
divine in its nature than the material on which it works, it is better
that the superior principle should be separated from the inferior.
Therefore, wherever it is possible and so far as it is possible, the
male is separated from the female. For the first principle of the
movement, or efficient cause, whereby that which comes into being is
male, is better and more divine than the material whereby it is
female. The male, however, comes together and mingles with the
female for the work of generation, because this is common to both.

  A thing lives, then, in virtue of participating in the male and
female principles, wherefore even plants have some kind of life; but
the class of animals exists in virtue of sense-perception. The sexes
are divided in nearly all of these that can move about, for the
reasons already stated, and some of them, as said before, emit semen
in copulation, others not. The reason of this is that the higher
animals are more independent in their nature, so that they have
greater size, and this cannot exist without vital heat; for the
greater body requires more force to move it, and heat is a motive
force. Therefore, taking a general view, we may say that sanguinea are
of greater size than bloodless animals, and those which move about
than those which remain fixed. And these are just the animals which
emit semen on account of their heat and size.

  So much for the cause of the existence of the two sexes. Some
animals bring to perfection and produce into the world a creature like
themselves, as all those which bring their young into the world alive;
others produce something undeveloped which has not yet acquired its
own form; in this latter division the sanguinea lay eggs, the
bloodless animals either lay an egg or give birth to a scolex. The
difference between egg and scolex is this: an egg is that from a
part of which the young comes into being, the rest being nutriment for
it; but the whole of a scolex is developed into the whole of the young
animal. Of the vivipara, which bring into the world an animal like
themselves, some are internally viviparous  (as men, horses, cattle,
and of marine animals dolphins and the other cetacea);  others first
lay eggs within themselves, and only after this are externally
viviparous  (as the cartilaginous fishes).  Among the ovipara some
produce the egg in a perfect condition  (as birds and all oviparous
quadrupeds and footless animals, e.g. lizards and tortoises and most
snakes; for the eggs of all these do not increase when once laid).
The eggs of others are imperfect; such are those of fishes,
crustaceans, and cephalopods, for their eggs increase after being
produced.

  All the vivipara are sanguineous, and the sanguinea are either
viviparous or oviparous, except those which are altogether
infertile. Among bloodless animals the insects produce a scolex, alike
those that are generated by copulation and those that copulate
themselves though not so generated. For there are some insects of this
sort, which though they come into being by spontaneous generation
are yet male and female; from their union something is produced,
only it is imperfect; the reason of this has been previously stated.

  These classes admit of much cross-division. Not all bipeds are
viviparous  (for birds are oviparous),  nor are they all oviparous
(for man is viviparous),  nor are all quadrupeds oviparous  (for
horses, cattle, and countless others are viviparous),  nor are they
all viviparous  (for lizards, crocodiles, and many others lay eggs).

 Nor does the presence or absence of feet make the difference
between them, for not only are some footless animals viviparous, as
vipers and the cartilaginous fishes, while others are oviparous, as
the other fishes and serpents, but also among those which have feet
many are oviparous and many viviparous, as the quadrupeds above
mentioned. And some which have feet, as man, and some which have
not, as the whale and dolphin, are internally viviparous. By this
character then it is not possible to divide them, nor is any of the
locomotive organs the cause of this difference, but it is those
animals which are more perfect in their nature and participate in a
purer element which are viviparous, for nothing is internally
viviparous unless it receive and breathe out air. But the more perfect
are those which are hotter in their nature and have more moisture
and are not earthy in their composition. And the measure of natural
heat is the lung when it has blood in it, for generally those
animals which have a lung are hotter than those which have not, and in
the former class again those whose lung is not spongy nor solid nor
containing only a little blood, but soft and full of blood. And as the
animal is perfect but the egg and the scolex are imperfect, so the
perfect is naturally produced from the more perfect. If animals are
hotter as shown by their possessing a lung but drier in their
nature, or are colder but have more moisture, then they either lay a
perfect egg or are viviparous after laying an egg within themselves.
For birds and scaly reptiles because of their heat produce a perfect
egg, but because of their dryness it is only an egg; the cartilaginous
fishes have less heat than these but more moisture, so that they are
intermediate, for they are both oviparous and viviparous within
themselves, the former because they are cold, the latter because of
their moisture; for moisture is vivifying, whereas dryness is furthest
removed from what has life. Since they have neither feathers nor
scales such as either reptiles or other fishes have, all which are
signs rather of a dry and earthy nature, the egg they produce is soft;
for the earthy matter does not come to the surface in their eggs any
more than in themselves. This is why they lay eggs in themselves,
for if the egg were laid externally it would be destroyed, having no
protection.

  Animals that are cold and rather dry than moist also lay eggs, but
the egg is imperfect; at the same time, because they are of an
earthy nature and the egg they produce is imperfect, therefore it
has a hard integument that it may be preserved by the protection of
the shell-like covering. Hence fishes, because they are scaly, and
crustacea, because they are of an earthy nature, lay eggs with a
hard integument.

  The cephalopods, having themselves bodies of a sticky nature,
preserve in the same way the imperfect eggs they lay, for they deposit
a quantity of sticky material about the embryo. All insects produce
a scolex. Now all the insects are bloodless, wherefore all creatures
that produce a scolex from themselves are so. But we cannot say simply
that all bloodless animals produce a scolex, for the classes overlap
one another, (1) the insects, (2) the animals that produce a scolex,
(3) those that lay their egg imperfect, as the scaly fishes, the
crustacea, and the cephalopoda. I say that these form a gradation, for
the eggs of these latter resemble a scolex, in that they increase
after oviposition, and the scolex of insects again as it develops
resembles an egg; how so we shall explain later.

  We must observe how rightly Nature orders generation in regular
gradation. The more perfect and hotter animals produce their young
perfect in respect of quality  (in respect of quantity this is so with
no animal, for the young always increase in size after birth),  and
these generate living animals within themselves from the first. The
second class do not generate perfect animals within themselves from
the first  (for they are only viviparous after first laying eggs),
but still they are externally viviparous. The third class do not
produce a perfect animal, but an egg, and this egg is perfect. Those
whose nature is still colder than these produce an egg, but an
imperfect one, which is perfected outside the body, as the class of
scaly fishes, the crustacea, and the cephalopods. The fifth and
coldest class does not even lay an egg from itself; but so far as
the young ever attain to this condition at all, it is outside the body
of the parent, as has been said already. For insects produce a
scolex first; the scolex after developing becomes egg-like  (for the
so-called chrysalis or pupa is equivalent to an egg);  then from
this it is that a perfect animal comes into being, reaching the end of
its development in the second change.

  Some animals then, as said before, do not come into being from
semen, but all the sanguinea do so which are generated by
copulation, the male emitting semen into the female when this has
entered into her the young are formed and assume their peculiar
character, some within the animals themselves when they are
viviparous, others in eggs.

  There is a considerable difficulty in understanding how the plant is
formed out of the seed or any animal out of the semen. Everything that
comes into being or is made must (1) be made out of something, (2)
be made by the agency of something, and (3) must become something. Now
that out of which it is made is the material; this some animals have
in its first form within themselves, taking it from the female parent,
as all those which are not born alive but produced as a scolex or an
egg; others receive it from the mother for a long time by sucking,
as the young of all those which are not only externally but also
internally viviparous. Such, then, is the material out of which things
come into being, but we now are inquiring not out of what the parts of
an animal are made, but by what agency. Either it is something
external which makes them, or else something existing in the seminal
fluid and the semen; and this must either be soul or a part of soul,
or something containing soul.

  Now it would appear irrational to suppose that any of either the
internal organs or the other parts is made by something external,
since one thing cannot set up a motion in another without touching it,
nor can a thing be affected in any way by another if it does not set
up a motion in it. Something then of the sort we require exists in the
embryo itself, being either a part of it or separate from it. To
suppose that it should be something else separate from it is
irrational. For after the animal has been produced does this something
perish or does it remain in it? But nothing of the kind appears to
be in it, nothing which is not a part of the whole plant or animal.
Yet, on the other hand, it is absurd to say that it perishes after
making either all the parts or only some of them. If it makes some
of the parts and then perishes, what is to make the rest of them?
Suppose this something makes the heart and then perishes, and the
heart makes another organ, by the same argument either all the parts
must perish or all must remain. Therefore it is preserved and does not
perish. Therefore it is a part of the embryo itself which exists in
the semen from the beginning; and if indeed there is no part of the
soul which does not exist in some part of the body, it would also be a
part containing soul in it from the beginning.

  How, then, does it make the other parts? Either all the parts, as
heart, lung, liver, eye, and all the rest, come into being together or
in succession, as is said in the verse ascribed to Orpheus, for
there he says that an animal comes into being in the same way as the
knitting of a net. That the former is not the fact is plain even to
the senses, for some of the parts are clearly visible as already
existing in the embryo while others are not; that it is not because of
their being too small that they are not visible is clear, for the lung
is of greater size than the heart, and yet appears later than the
heart in the original development. Since, then, one is earlier and
another later, does the one make the other, and does the later part
exist on account of the part which is next to it, or rather does the
one come into being only after the other? I mean, for instance, that
it is not the fact that the heart, having come into being first,
then makes the liver, and the liver again another organ, but that
the liver only comes into being after the heart, and not by the agency
of the heart, as a man becomes a man after being a boy, not by his
agency. An explanation of this is that, in all the productions of
Nature or of art, what already exists potentially is brought into
being only by what exists actually; therefore if one organ formed
another the form and the character of the later organ would have to
exist in the earlier, e.g. the form of the liver in the heart. And
otherwise also the theory is strange and fictitious.

  Yet again, if the whole animal or plant is formed from semen or
seed, it is impossible that any part of it should exist ready made
in the semen or seed, whether that part be able to make the other
parts or no. For it is plain that, if it exists in it from the
first, it was made by that which made the semen. But semen must be
made first, and that is the function of the generating parent. So,
then, it is not possible that any part should exist in it, and
therefore it has not within itself that which makes the parts.

  But neither can this agent be external, and yet it must needs be one
or other of the two. We must try, then, to solve this difficulty,
for perhaps some one of the statements made cannot be made without
qualification, e.g. the statement that the parts cannot be made by
what is external to the semen. For if in a certain sense they
cannot, yet in another sense they can.  (Now it makes no difference
whether we say &#39;the semen&#39; or &#39;that from which the semen comes&#39;, in so
far as the semen has in itself the movement initiated by the other.)

 It is possible, then, that A should move B, and B move C; that, in
fact, the case should be the same as with the automatic machines shown
as curiosities. For the parts of such machines while at rest have a
sort of potentiality of motion in them, and when any external force
puts the first of them in motion, immediately the next is moved in
actuality. As, then, in these automatic machines the external force
moves the parts in a certain sense  (not by touching any part at the
moment, but by having touched one previously),  in like manner also
that from which the semen comes, or in other words that which made the
semen, sets up the movement in the embryo and makes the parts of it by
having first touched something though not continuing to touch it. In a
way it is the innate motion that does this, as the act of building
builds the house. Plainly, then, while there is something which
makes the parts, this does not exist as a definite object, nor does it
exist in the semen at the first as a complete part.

  But how is each part formed? We must answer this by starting in
the first instance from the principle that, in all products of
Nature or art, a thing is made by something actually existing out of
that which is potentially such as the finished product. Now the
semen is of such a nature, and has in it such a principle of motion,
that when the motion is ceasing each of the parts comes into being,
and that as a part having life or soul. For there is no such thing
as face or flesh without life or soul in it; it is only equivocally
that they will be called face or flesh if the life has gone out of
them, just as if they had been made of stone or wood. And the
homogeneous parts and the organic come into being together. And just
as we should not say that an axe or other instrument or organ was made
by the fire alone, so neither shall we say that foot or hand were made
by heat alone. The same applies also to flesh, for this too has a
function. While, then, we may allow that hardness and softness,
stickiness and brittleness, and whatever other qualities are found
in the parts that have life and soul, may be caused by mere heat and
cold, yet, when we come to the principle in virtue of which flesh is
flesh and bone is bone, that is no longer so; what makes them is the
movement set up by the male parent, who is in actuality what that
out of which the offspring is made is in potentiality. This is what we
find in the products of art; heat and cold may make the iron soft
and hard, but what makes a sword is the movement of the tools
employed, this movement containing the principle of the art. For the
art is the starting-point and form of the product; only it exists in
something else, whereas the movement of Nature exists in the product
itself, issuing from another nature which has the form in actuality.

  Has the semen soul, or not? The same argument applies here as in the
question concerning the parts. As no part, if it participate not in
soul, will be a part except in an equivocal sense  (as the eye of a
dead man is still called an &#39;eye&#39;),  so no soul will exist in anything
except that of which it is soul; it is plain therefore that semen both
has soul, and is soul, potentially.

  But a thing existing potentially may be nearer or further from its
realization in actuality, as e.g. a mathematician when asleep is
further from his realization in actuality as engaged in mathematics
than when he is awake, and when awake again but not studying
mathematics he is further removed than when he is so studying.
Accordingly it is not any part that is the cause of the soul&#39;s
coming into being, but it is the first moving cause from outside.
(For nothing generates itself, though when it has come into being it
thenceforward increases itself.)  Hence it is that only one part comes
into being first and not all of them together. But that must first
come into being which has a principle of increase  (for this nutritive
power exists in all alike, whether animals or plants, and this is
the same as the power that enables an animal or plant to generate
another like itself, that being the function of them all if
naturally perfect).  And this is necessary for the reason that
whenever a living thing is produced it must grow. It is produced,
then, by something else of the same name, as e.g. man is produced by
man, but it is increased by means of itself. There is, then, something
which increases it. If this is a single part, this must come into
being first. Therefore if the heart is first made in some animals, and
what is analogous to the heart in the others which have no heart, it
is from this or its analogue that the first principle of movement
would arise.

  We have thus discussed the difficulties previously raised on the
question what is the efficient cause of generation in each case, as
the first moving and formative power.

                                 2

  The next question to be mooted concerns the nature of semen. For
whereas when it issues from the animal it is thick and white, yet on
cooling it becomes liquid as water, and its colour is that of water.
This would appear strange, for water is not thickened by heat; yet
semen is thick when it issues from within the animal&#39;s body which is
hot, and becomes liquid on cooling. Again, watery fluids freeze, but
semen, if exposed in frosts to the open air, does not freeze but
liquefies, as if it was thickened by the opposite of cold. Yet it is
unreasonable, again, to suppose that it is thickened by heat. For it
is only substances having a predominance of earth in their composition
that coagulate and thicken on boiling, e.g. milk. It ought then to
solidify on cooling, but as a matter of fact it does not become
solid in any part but the whole of it goes like water.

  This then is the difficulty. If it is water, water evidently does
not thicken through heat, whereas the semen is thick and both it and
the body whence it issues are hot. If it is made of earth or a mixture
of earth and water, it ought not to liquefy entirely and turn to
water.

  Perhaps, however, we have not discriminated all the possibilities.
It is not only the liquids composed of water and earthy matter that
thicken, but also those composed of water and air; foam, for instance,
becomes thicker and white, and the smaller and less visible the
bubbles in it, the whiter and firmer does the mass appear. The same
thing happens also with oil; on mixing with air it thickens, wherefore
that which is whitening becomes thicker, the watery part in it being
separated off by the heat and turning to air. And if oxide of lead
is mixed with water or even with oil, the mass increases greatly and
changes from liquid and dark to firm and white, the reason being
that air is mixed in with it which increases the mass and makes the
white shine through, as in foam and snow  (for snow is foam).  And
water itself on mingling with oil becomes thick and white, because air
is entangled in it by the act of pounding them together, and oil
itself has much air in it  (for shininess is a property of air, not of
earth or water).  This too is why it floats on the surface of the
water, for the air contained in it as in a vessel bears it up and
makes it float, being the cause of its lightness. So too oil is
thickened without freezing in cold weather and frosts; it does not
freeze because of its heat  (for the air is hot and will not freeze),
but because the air is forced together and compressed, as..., by the
cold, the oil becomes thicker. These are the reasons why semen is firm
and white when it issues from within the animal; it has a quantity
of hot air in it because of the internal heat; afterwards, when the
heat has evaporated and the air has cooled, it turns liquid and
dark; for the water, and any small quantity of earthy matter there may
be, remain in semen as it dries, as they do in phlegm.

  Semen, then, is a compound of spirit  (pneuma)  and water, and the
former is hot air  (aerh);  hence semen is liquid in its nature
because it is made of water. What Ctesias the Cnidian has asserted
of the semen of elephants is manifestly untrue; he says that it
hardens so much in drying that it becomes like amber. But this does
not happen, though it is true that one semen must be more earthy
than another, and especially so with animals that have much earthy
matter in them because of the bulk of their bodies. And it is thick
and white because it is mixed with spirit, for it is also an
invariable rule that it is white, and Herodotus does not report the
truth when he says that the semen of the Aethiopians is black, as if
everything must needs be black in those who have a black skin, and
that too when he saw their teeth were white. The reason of the
whiteness of semen is that it is a foam, and foam is white, especially
that which is composed of the smallest parts, small in the sense
that each bubble is invisible, which is what happens when water and
oil are mixed and shaken together, as said before.  (Even the ancients
seem to have noticed that semen is of the nature of foam; at least
it was from this they named the goddess who presides over union.)

  This then is the explanation of the problem proposed, and it is
plain too that this is why semen does not freeze; for air will not
freeze.

                                 3

  The next question to raise and to answer is this. If, in the case of
those animals which emit semen into the female, that which enters
makes no part of the resulting embryo, where is the material part of
it diverted if  (as we have seen)  it acts by means of the power
residing in it? It is not only necessary to decide whether what is
forming in the female receives anything material, or not, from that
which has entered her, but also concerning the soul in virtue of which
an animal is so called  (and this is in virtue of the sensitive part
of the soul)- does this exist originally in the semen and in the
unfertilized embryo or not, and if it does whence does it come? For
nobody would put down the unfertilized embryo as soulless or in
every sense bereft of life  (since both the semen and the embryo of an
animal have every bit as much life as a plant),  and it is
productive up to a certain point. That then they possess the nutritive
soul is plain  (and plain is it from the discussions elsewhere about
soul why this soul must be acquired first).  As they develop they also
acquire the sensitive soul in virtue of which an animal is an
animal. For e.g. an animal does not become at the same time an
animal and a man or a horse or any other particular animal. For the
end is developed last, and the peculiar character of the species is
the end of the generation in each individual. Hence arises a
question of the greatest difficulty, which we must strive to solve
to the best of our ability and as far as possible. When and how and
whence is a share in reason acquired by those animals that participate
in this principle? It is plain that the semen and the unfertilized
embryo, while still separate from each other, must be assumed to
have the nutritive soul potentially, but not actually, except that
(like those unfertilized embryos that are separated from the mother)

 it absorbs nourishment and performs the function of the nutritive
soul. For at first all such embryos seem to live the life of a
plant. And it is clear that we must be guided by this in speaking of
the sensitive and the rational soul. For all three kinds of soul,
not only the nutritive, must be possessed potentially before they
are possessed in actuality. And it is necessary either (1) that they
should all come into being in the embryo without existing previously
outside it, or (2) that they should all exist previously, or (3), that
some should so exist and others not. Again, it is necessary that
they should either (1) come into being in the material supplied by the
female without entering with the semen of the male, or (2) come from
the male and be imparted to the material in the female. If the latter,
then either all of them, or none, or some must come into being in
the male from outside.

  Now that it is impossible for them all to preexist is clear from
this consideration. Plainly those principles whose activity is
bodily cannot exist without a body, e.g. walking cannot exist
without feet. For the same reason also they cannot enter from outside.
For neither is it possible for them to enter by themselves, being
inseparable from a body, nor yet in a body, for the semen is only a
secretion of the nutriment in process of change. It remains, then, for
the reason alone so to enter and alone to be divine, for no bodily
activity has any connexion with the activity of reason.

  Now it is true that the faculty of all kinds of soul seems to have a
connexion with a matter different from and more divine than the
so-called elements; but as one soul differs from another in honour and
dishonour, so differs also the nature of the corresponding matter. All
have in their semen that which causes it to be productive; I mean what
is called vital heat. This is not fire nor any such force, but it is
the spiritus included in the semen and the foam-like, and the
natural principle in the spiritus, being analogous to the element of
the stars. Hence, whereas fire generates no animal and we do not
find any living thing forming in either solids or liquids under the
influence of fire, the heat of the sun and that of animals does
generate them. Not only is this true of the heat that works through
the semen, but whatever other residuum of the animal nature there
may be, this also has still a vital principle in it. From such
considerations it is clear that the heat in animals neither is fire
nor derives its origin from fire.

  Let us return to the material of the semen, in and with which
comes away from the male the spiritus conveying the principle of soul.
Of this principle there are two kinds; the one is not connected with
matter, and belongs to those animals in which is included something
divine  (to wit, what is called the reason),  while the other is
inseparable from matter. This material of the semen dissolves and
evaporates because it has a liquid and watery nature. Therefore we
ought not to expect it always to come out again from the female or
to form any part of the embryo that has taken shape from it; the
case resembles that of the fig-juice which curdles milk, for this
too changes without becoming any part of the curdling masses.

  It has been settled, then, in what sense the embryo and the semen
have soul, and in what sense they have not; they have it potentially
but not actually.

  Now semen is a secretion and is moved with the same movement as that
in virtue of which the body increases  (this increase being due to
subdivision of the nutriment in its last stage).  When it has
entered the uterus it puts into form the corresponding secretion of
the female and moves it with the same movement wherewith it is moved
itself. For the female&#39;s contribution also is a secretion, and has all
the arts in it potentially though none of them actually; it has in
it potentially even those parts which differentiate the female from
the male, for just as the young of mutilated parents are sometimes
born mutilated and sometimes not, so also the young born of a female
are sometimes female and sometimes male instead. For the female is, as
it were, a mutilated male, and the catamenia are semen, only not pure;
for there is only one thing they have not in them, the principle of
soul. For this reason, whenever a wind-egg is produced by any
animal, the egg so forming has in it the parts of both sexes
potentially, but has not the principle in question, so that it does
not develop into a living creature, for this is introduced by the
semen of the male. When such a principle has ben imparted to the
secretion of the female it becomes an embryo.

  Liquid but corporeal substances become surrounded by some kind of
covering on heating, like the solid scum which forms on boiled foods
when cooling. All bodies are held together by the glutinous; this
quality, as the embryo develops and increases in size, is acquired
by the sinewy substance, which holds together the parts of animals,
being actual sinew in some and its analogue in others. To the same
class belong also skin, blood-vessels, membranes, and the like, for
these differ in being more or less glutinous and generally in excess
and deficiency.

                                 4

  In those animals whose nature is comparatively imperfect, when a
perfect embryo  (which, however, is not yet a perfect animal)  has
been formed, it is cast out from the mother, for reasons previously
stated. An embryo is then complete when it is either male or female,
in the case of those animals who possess this distinction, for some
(i.e. all those which are not themselves produced from a male or
female parent nor from a union of the two)  produce an offspring which
is neither male nor female. Of the generation of these we shall
speak later.

  The perfect animals, those internally viviparous, keep the
developing embryo within themselves and in close connexion until
they give birth to a complete animal and bring it to light.

  A third class is externally viviparous but first internally
oviparous; they develop the egg into a perfect condition, and then
in some cases the egg is set free as with creatures externally
oviparous, and the animal is produced from the egg within the mother&#39;s
body; in other cases, when the nutriment from the egg is consumed,
development is completed by connection with the uterus, and
therefore the egg is not set free from the uterus. This character
marks the cartilaginous fish, of which we must speak later by
themselves.

  Here we must make our first start from the first class; these are
the perfect or viviparous animals, and of these the first is man.
Now the secretion of the semen takes place in all of them just as does
that of any other residual matter. For each is conveyed to its
proper place without any force from the breath or compulsion of any
other cause, as some assert, saying that the generative parts
attract the semen like cupping-glasses, aided by the force of the
breath, as if it were possible for either this secretion or the
residue of the solid and liquid nutriment to go anywhere else than
they do without the exertion of such a force. Their reason is that the
discharge of both is attended by holding the breath, but this is a
common feature of all cases when it is necessary to move anything,
because strength arises through holding the breath. Why, even
without this force the secretions or excretions are discharged in
sleep if the parts concerned are full of them and are relaxed. One
might as well say that it is by the breath that the seeds of plants
are always segregated to the places where they are wont to bear fruit.
No, the real cause, as has been stated already, is that there are
special parts for receiving all the secretions, alike the useless  (as
the residues of the liquid and solid nutriment),  and the blood, which
has the so-called blood-vessels.

  To consider now the region of the uterus in the female- the two
blood-vessels, the great vessel and the aorta, divide higher up, and
many fine vessels from them terminate in the uterus. These become
over-filled from the nourishment they convey, nor is the female nature
able to concoct it, because it is colder than man&#39;s; so the blood is
excreted through very fine vessels into the uterus, these being unable
on account of their narrowness to receive the excessive quantity,
and the result is a sort of haemorrhage. The period is not
accurately defined in women, but tends to return during the waning
of the moon. This we should expect, for the bodies of animals are
colder when the environment happens to become so, and the time of
change from one month to another is cold because of the absence of the
moon, whence also it results that this time is stormier than the
middle of the month. When then the residue of the nourishment has
changed into blood, the catamenia tend to occur at the above-mentioned
period, but when it is not concocted a little matter at a time is
always coming away, and this is why &#39;whites&#39; appear in females while
still small, in fact mere children. If both these discharges of the
secretions are moderate, the body remains in good health, for they act
as a purification of the secretions which are the causes of a morbid
state of body; if they do not occur at all or if they are excessive,
they are injurious, either causing illness or pulling down the
patient; hence whites, if continuous and excessive, prevent girls from
growing. This secretion then is necessarily discharged by females
for the reasons given; for, the female nature being unable to
concoct the nourishment thoroughly, there must not only be left a
residue of the useless nutriment, but also there must be a residue
in the blood-vessels, and this filling the channels of the finest
vessels must overflow. Then Nature, aiming at the best end, uses it up
in this place for the sake of generation, that another creature may
come into being of the same kind as the former was going to be, for
the menstrual blood is already potentially such as the body from which
it is discharged.

  In all females, then, there must necessarily be such a secretion,
more indeed in those that have blood and of these most of all in
man, but in the others also some matter must be collected in the
uterine region. The reason why there is more in those that have
blood and most in man has been already given, but why, if all
females have such a secretion, have not all males one to correspond?
For some of them do not emit semen but, just as those which do emit it
fashion by the movement in the semen the mass forming from the
material supplied by the female, so do the animals in question bring
the same to pass and exert the same formative power by the movement
within themselves in that part from whence the semen is secreted. This
is the region about the diaphragm in all those animals which have one,
for the heart or its analogue is the first principle of a natural
body, while the lower part is a mere addition for the sake of it.
Now the reason why it is not all males that have a generative
secretion, while all females do, is that the animal is a body with
Soul or life; the female always provides the material, the male that
which fashions it, for this is the power that we say they each
possess, and this is what is meant by calling them male and female.
Thus while it is necessary for the female to provide a body and a
material mass, it is not necessary for the male, because it is not
within the work of art or the embryo that the tools or the maker
must exist. While the body is from the female, it is the soul that
is from the male, for the soul is the reality of a particular body.
For this reason if animals of a different kind are crossed  (and
this is possible when the periods of gestation are equal and
conception takes place nearly at the same season and there is no great
difference in the of the animals),  the first cross has a common
resemblance to both parents, as the hybrid between fox and dog,
partridge and domestic fowl, but as time goes on and one generation
springs from another, the final result resembles the female in form,
just as foreign seeds produce plants varying in accordance with the
country in which they are sown. For it is the soil that gives to the
seeds the material and the body of the plant. And hence the part of
the female which receives the semen is not a mere passage, but the
uterus has a considerable width, whereas the males that emit semen
have only passages for this purpose, and these are bloodless.

  Each of the secretions becomes such at the moment when it is in
its proper place; before that there is nothing of the sort unless with
much violence and contrary to nature.

  We have thus stated the reason for which the generative secretions
are formed in animals. But when the semen from the male  (in those
animals which emit semen)  has entered, it puts into form the purest
part of the female secretion  (for the greater part of the catamenia
also is useless and fluid, as is the most fluid part of the male
secretion, i.e. in a single emission, the earlier discharge being in
most cases apt to be infertile rather than the later, having less
vital heat through want of concoction, whereas that which is concocted
is thick and of a more material nature).

  If there is no external discharge, either in women or other animals,
on account of there not being much useless and superfluous matter in
the secretion, then the quantity forming within the female
altogether is as much as what is retained within those animals which
have an external discharge; this is put into form by the power of
the male residing in the semen secreted by him, or, as is clearly seen
to happen in some insects, by the part in the female analogous to
the uterus being inserted into the male.

  It has been previously stated that the discharge accompanying sexual
pleasure in the female contributes nothing to the embryo. The chief
argument for the opposite view is that what are called bad dreams
occur by night with women as with men; but this is no proof, for the
same thing happens to young men also who do not yet emit semen, and to
those who do emit semen but whose semen is infertile.

  It is impossible to conceive without the emission of the male in
union and without the secretion of the corresponding female
material, whether it be discharged externally or whether there is only
enough within the body. Women conceive, however, without
experiencing the pleasure usual in such intercourse, if the part
chance to be in heat and the uterus to have descended. But generally
speaking the opposite is the case, because the os uteri is not
closed when the discharge takes place which is usually accompanied
by pleasure in women as well as men, and when this is so there is a
readier way for the semen of the male to be drawn into the uterus.

  The actual discharge does not take place within the uterus as some
think, the os uteri being too narrow, but it is in the region in front
of this, where the female discharges the moisture found in some cases,
that the male emits the semen. Sometimes it remains in this place;
at other times, if the uterus chance to be conveniently placed and hot
on account of the purgation of the catamenia, it draws it within
itself. A proof of this is that pessaries, though wet when applied,
are removed dry. Moreover, in all those animals which have the
uterus near the hypozoma, as birds and viviparous fishes, it is
impossible that the semen should be so discharged as to enter it; it
must be drawn into it. This region, on account of the heat which is in
it, attracts the semen. The discharge and collection of the
catamenia also excite heat in this part. Hence it acts like
cone-shaped vessels which, when they have been washed out with hot
water, their mouth being turned downwards, draw water into themselves.
And this is the way things are drawn up, but some say that nothing
of the kind happens with the organic parts concerned in copulation.
Precisely the opposite is the case of those who say the woman emits
semen as well as the man, for if she emits it outside the uterus
this must then draw it back again into itself if it is to be mixed
with the semen of the male. But this is a superfluous proceeding,
and Nature does nothing superfluous.

  When the material secreted by the female in the uterus has been
fixed by the semen of the male  (this acts in the same way as rennet
acts upon milk, for rennet is a kind of milk containing vital heat,
which brings into one mass and fixes the similar material, and the
relation of the semen to the catamenia is the same, milk and the
catamenia being of the same nature)- when, I say, the more solid
part comes together, the liquid is separated off from it, and as the
earthy parts solidify membranes form all round it; this is both a
necessary result and for a final cause, the former because the surface
of a mass must solidify on heating as well as on cooling, the latter
because the foetus must not be in a liquid but be separated from it.
Some of these are called membranes and others choria, the difference
being one of more or less, and they exist in ovipara and vivipara
alike.

  When the embryo is once formed, it acts like the seeds of plants.
For seeds also contain the first principle of growth in themselves,
and when this  (which previously exists in them only potentially)  has
been differentiated, the shoot and the root are sent off from it,
and it is by the root that the plant gets nourishment; for it needs
growth. So also in the embryo all the parts exist potentially in a way
at the same time, but the first principle is furthest on the road to
realization. Therefore the heart is first differentiated in actuality.
This is clear not only to the senses  (for it is so)  but also on
theoretical grounds. For whenever the young animal has been
separated from both parents it must be able to manage itself, like a
son who has set up house away from his father. Hence it must have a
first principle from which comes the ordering of the body at a later
stage also, for if it is to come in from outside at later period to
dwell in it, not only may the question be asked at what time it is
to do so, but also we may object that, when each of the parts is
separating from the rest, it is necessary that this principle should
exist first from which comes growth and movement to the other parts.

 (Wherefore all who say, as did Democritus, that the external parts of
animals are first differentiated and the internal later, are much
mistaken; it is as if they were talking of animals of stone or wood.
For such as these have no principle of growth at all, but all
animals have, and have it within themselves.)  Therefore it is that
the heart appears first distinctly marked off in all the sanguinea,
for this is the first principle or origin of both homogeneous and
heterogeneous parts, since from the moment that the animal or organism
needs nourishment, from that moment does this deserve to be called its
principle or origin. For the animal grows, and the nutriment, in its
final stage, of an animal is the blood or its analogue, and of this
the blood-vessels are the receptacle, wherefore the heart is the
principle or origin of these also.  (This is clear from the
Enquiries and the anatomical drawings.)

  Since the embryo is already potentially an animal but an imperfect
one, it must obtain its nourishment from elsewhere; accordingly it
makes use of the uterus and the mother, as a plant does of the
earth, to get nourishment, until it is pe