Various Works

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
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  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,