by Aristotle
namely that there may be no impediment to the swelling which
necessarily occurs in the food as it gets heated, nor to the expansion
of the womb in pregnancy.
At the extreme end of what is called the trunk are the parts
concerned in the evacuation of the solid and also of the fluid
residue. In all sanguineous animals with some few exceptions, and in
all Vivipara without any exception at all, the same part which
serves for the evacuation of the fluid residue is also made by
nature to serve in sexual congress, and this alike in male and female.
For the semen is a kind of fluid and residual matter. The proof of
this will be given hereafter, but for the present let it taken for
granted. (The like holds good of the menstrual fluid in women, and
of the part where they emit semen. This also, however, is a matter
of which a more accurate account will be given hereafter. For the
present let it be simply stated as a fact, that the catamenia of the
female like the semen of the male are residual matter. Both of them,
moreover, being fluid, it is only natural that the parts which serve
for voidance of the urine should give issue to residues which resemble
it in character.) Of the internal structure of these parts, and of the
differences which exist between the parts concerned with semen and the
parts concerned with conception, a clear account is given in the
book of Researches concerning Animals and in the treatises on Anatomy.
Moreover, I shall have to speak of them again when I come to deal with
Generation. As regards, however, the external shape of these parts, it
is plain enough that they are adapted to their operations, as indeed
of necessity they must be. There are, however, differences in the male
organ corresponding to differences in the body generally. For all
animals are not of an equally sinewy nature. This organ, again, is the
only one that, independently of any morbid change, admits of
augmentation and of diminution of bulk. The former condition is of
service in copulation, while the other is required for the advantage
of the body at large. For, were the organ constantly in the former
condition, it would be an incumbrance. The organ therefore has been
formed of such constituents as will admit of either state. For it is
partly sinewy, partly cartilaginous, and thus is enabled either to
contract or to become extended, and is capable of admitting air.
All female quadrupeds void their urine backwards, because the
position of the parts which this implies is useful to them in the
act of copulation. This is the case with only some few males, such
as the lynx, the lion, the camel, and the hare. No quadruped with a
solid hoof is retromingent.
The posterior portion of the body and the parts about the legs are
peculiar in man as compared with quadrupeds. Nearly all these latter
have a tail, and this whether they are viviparous or oviparous. For,
even if the tail be of no great size, yet they have a kind of scut, as
at any rate a small representative of it. But man is tail-less. He
has, however, buttocks, which exist in none of the quadrupeds. His
legs also are fleshy (as too are his thighs and feet); while the
legs in all other animals that have any, whether viviparous or not,
are fleshless, being made of sinew and bone and spinous substance. For
all these differences there is, so to say, one common explanation, and
this is that of all animals man alone stands erect. It was to
facilitate the maintenance of this position that Nature made his upper
parts light, taking away some of their corporeal substance, and
using it to increase the weight of lithe parts below, so that the
buttocks, the thighs, and the calves of the legs were all made fleshy.
The character which she thus gave to the buttocks renders them at
the same time useful in resting the body. For standing causes no
fatigue to quadrupeds, and even the long continuance of this posture
produces in them no weariness; for they are supported the whole time
by four props, which is much as though they were lying down. But to
man it is no task to remain for any length of time on his feet, his
body demanding rest in a sitting position. This, then, is the reason
why man has buttocks and fleshy legs; and the presence of these fleshy
parts explains why he has no tail. For the nutriment which would
otherwise go to the tail is used up in the production of these
parts, while at the same time the existence of buttocks does away with
the necessity of a tail. But in quadrupeds and other animals the
reverse obtains. For they are of dwarf-like form, so that all the
pressure of their weight and corporeal substance is on their upper
part, and is withdrawn from the parts below. On this account they
are without buttocks and have hard legs. In order, however, to cover
and protect that part which serves for the evacuation of excrement,
nature has given them a tail of some kind or other, subtracting for
the purpose some of the nutriment which would otherwise go to the
legs. Intermediate in shape between man and quadrupeds is the ape,
belonging therefore to neither or to both, and having on this
account neither tail nor buttocks; no tail in its character of
biped, no buttocks in its character of quadruped. There is great
diversity of so-called tails; and this organ like others is
sometimes used by nature for by-purposes, being made to serve not only
as a covering and protection to the fundament, but also for other uses
and advantages of its possessor.
There are differences in the feet of quadrupeds. For in some of
these animals there is a solid hoof, and in others a hoof cloven
into two, and again in others a foot divided into many parts.
The hoof is solid when the body is large and the earthy matter
present in great abundance; in which case the earth, instead of
forming teeth and horns, is separated in the character of a nail,
and being very abundant forms one continuous nail, that is a hoof,
in place of several. This consumption of the earthy matter on the hoof
explains why these animals, as a rule, have no huckle-bones; a
second reason being that the presence of such a bone in the joint of
the hind leg somewhat impedes its free motion. For extension and
flexion can be made more rapidly in parts that have but one angle than
in parts that have several. But the presence of a huckle-bone, as a
connecting bolt, is the introduction as it were of a new
limb-segment between the two ordinary ones. Such an addition adds to
the weight of the foot, but renders the act of progression more
secure. Thus it is that in such animals as have a hucklebone, it is
only in the posterior and not in the anterior limbs that this bone
is found. For the anterior limbs, moving as they do in advance of
the others, require to be light and capable of ready flexion,
whereas firmness and extensibility are what are wanted in the hind
limbs. Moreover, a huckle-bone adds weight to the blow of a limb,
and so renders it a suitable weapon of defence; and these animals
>
all use their hind legs to protect themselves, kicking out with
their heels against anything which annoys them. In the cloven-hoofed
quadrupeds the lighter character of the hind legs admits of there
being a huckle-bone; and the presence of the huckle-bone prevents them
from having a solid hoof, the bony substance remaining in the joint,
and therefore being deficient in the foot. As to the polydactylous
quadrupeds, none of them have huckle-bones. For if they had they would
not be polydactylous, but the divisions of the foot would only
extend to that amount of its breadth which was covered by the
huckle-bone. Thus it is that most of the animals that have
huckle-bones are cloven-hoofed.
Of all animals man has the largest foot in proportion to the size of
the body. This is only what might be expected. For seeing that he is
the only animal that stands erect, the two feet which are intended
to bear all the weight of the body must be both long and broad.
Equally intelligible is it that the proportion between the size of the
fingers and that of the whole hand should be inverted in the case of
the toes and feet. For the function of the hands is to take hold of
objects and retain them by pressure; so that the fingers require to be
long. For it is by its flexed portion that the hand grasps an
object. But the function of the feet is to enable us to stand
securely, and for this the undivided part of the foot requires to be
of larger size than the toes. However, it is better for the
extremity to be divided than to be undivided. For in an undivided foot
disease of any one part would extend to the whole organ; whereas, if
the foot be divided into separate digits, there is not an equal
liability to such an occurrence. The digits, again, by being short
would be less liable to injury. For these reasons the feet in man
are many-toed, while the separate digits are of no great length. The
toes, finally, are furnished with nails for the same reason as are the
fingers, namely because such projecting parts are weak and therefore
require special protection.
11
We have now done with such sanguineous animals as live on land and
bring forth their young alive; and, having dealt with all their main
kinds, we may pass on to such sanguineous animals as are oviparous. Of
these some have four feet, while others have none. The latter form a
single genus, namely the Serpents; and why these are apodous has
been already explained in the dissertation on Animal Progression.
Irrespective of this absence of feet, serpents resemble the
oviparous quadrupeds in their conformation.
In all these animals there is a head with its component parts; its
presence being determined by the same causes as obtain in the case
of other sanguineous animals; and in all, with the single exception of
the river crocodile, there is a tongue inside the mouth. In this one
exception there would seem to be no actual tongue, but merely a
space left vacant for it. The reason is that a crocodile is in a way a
land-animal and a water-animal combined. In its character of
land-animal it has a space for a tongue; but in its character of
water-animal it is without the tongue itself. For in some fishes, as
has already been mentioned, there is no appearance whatsoever of a
tongue, unless the mouth be stretched open very widely indeed; while
in others it is indistinctly separated from the rest of the mouth. The
reason for this is that a tongue would be of but little service to
such animals, seeing that they are unable to chew their food or to
taste it before swallowing, the pleasurable sensations they derive
from it being limited to the act of deglutition. For it is in their
passage down the gullet that solid edibles cause enjoyment, while it
is by the tongue that the savour of fluids is perceived. Thus it is
during deglutition that the oiliness, the heat, and other such
qualities of food are recognized; and, in fact, the satisfaction
from most solid edibles and dainties is derived almost entirely from
the dilatation of the oesophagus during deglutition. This sensation,
then, belongs even to animals that have no tongue, but while other
animals have in addition the sensations of taste, tongueless animals
have, we may say, no other satisfaction than it. What has now been
said explains why intemperance as regards drinks and savoury fluids
does not go hand in hand with intemperance as regards eating and solid
relishes.
In some oviparous quadrupeds, namely in lizards, the tongue is
bifid, as also it is in serpents, and its terminal divisions are of
hair-like fineness, as has already been described. (Seals also have
a forked tongue.) This it is which accounts for all these animals
being so fond of dainty food. The teeth in the four-footed Ovipara are
of the sharp interfitting kind, like the teeth of fishes. The organs
of all the senses are present and resemble those of other animals.
Thus there are nostrils for smell, eves for vision, and ears for
hearing. The latter organs, however, do not project from the sides
of the head, but consist simply of the duct, as also is the case in
birds. This is due in both cases to the hardness of the integument;
birds having their bodies covered with feathers, and these oviparous
quadrupeds with horny plates. These plates are equivalent to scales,
but of a harder character. This is manifest in tortoises and river
crocodiles, and also in the large serpents. For here the plates become
stronger than the bones, being seemingly of the same substance as
these.
These animals have no upper eyelid, but close the eye with the lower
lid In this they resemble birds, and the reason is the same as was
assigned in their case. Among birds there are some that can not only
thus close the eye, but can also blink by means of a membrane which
comes from its corner. But none of the oviparous quadrupeds blink; for
their eyes are harder than those of birds. The reason for this is that
keen vision and far-sightedness are of very considerable service to
birds, flying as they do in the air, whereas they would be of
comparatively small use to the oviparous quadrupeds, seeing that
they are all of troglodytic habits.
Of the two separate portions which constitute the head, namely the
upper part and the lower jaw, the latter in man and in the
viviparous quadrupeds moves not only upwards and downwards, but also
from side to side; while in fishes, and birds and oviparous
quadrupeds, the only movement is up and down. The reason is that
this latter movement is the one required in biting and dividing
food, while the lateral movement serve to reduce substances to a pulp.
To such animals, therefore, as have grinder-teeth this lateral
motion is of service; but to those animals that have no grinders it
would be quite useless, and they are therefore invariably without
it. For nature never makes anything that is superfluous. While in
all other animals it is the lower jaw that is movable, in the river
&n
bsp; crocodile it is exceptionally the upper. This is because the feet in
this creature are so excessively small as to be useless for seizing
and holding prey; on which account nature has given it a mouth that
can serve for these purposes in their stead. For that direction of
motion which will give the greater force to a blow will be the more
serviceable one in holding or in seizing prey; and a blow from above
is always more forcible than one from below. Seeing, then, that both
the prehension and the mastication of food are offices of the mouth,
and that the former of these two is the more essential in an animal
that has neither hands nor suitably formed feet, these crocodiles will
derive greater benefit from a motion of the upper jaw downwards than
from a motion of the lower jaw upwards. The same considerations
explain why crabs also move the upper division of each claw and not
the lower. For their claws are substitutes for hands, and so require
to be suitable for the prehension of food, and not for its
comminution; for such comminution and biting is the office of teeth.
In crabs, then, and in such other animals as are able to seize their
food in a leisurely manner, inasmuch as their mouth is not called on
to perform its office while they are still in the water, the two
functions are assigned to different parts, prehension to the hands
or feet, biting and comminution of food to the mouth. But in
crocodiles the mouth has been so framed by nature as to serve both
purposes, the jaws being made to move in the manner just described.
Another part present in these animals is a neck, this being the
necessary consequence of their having a lung. For the windpipe by
which the air is admitted to the lung is of some length. If,
however, the definition of a neck be correct, which calls it the
portion between the head and the shoulders, a serpent can scarcely
be said with the same right as the rest of these animals to have a
neck, but only to have something analogous to that part of the body.
It is a peculiarity of serpents, as compared with other animals allied
to them, that they are able to turn their head backwards without
stirring the rest of the body. The reason of this is that a serpent,