Aristotle · a new plain-English translation from the original language
1| [section 12] humans and others also the skins of other animals, do so with this same part. In these animals, then, the tongue is of this nature, standing in a kind of inverse relation to the trunk of elephants: for the trunk serves them for defense, and for these creatures the tongue takes the place of a sting. In the rest of the animals the tongue is in every case of the sort we have described. Book Three. [section 1] Next in order after what has been said comes the nature of the teeth in animals, and the mouth that is enclosed by them and composed of them. Now for animals generally the nature of the teeth serves, in common, the working of food, but apart from this, by kinds, some have them for the sake of strength — and this itself divides into acting and not being acted upon; for some animals have teeth for both purposes, both not to suffer harm and to inflict it, as do the wild animals whose nature is carnivorous, while others have them for the sake of defense only, as do many wild and tame animals besides. [section 2]
2| Man's teeth, for their common use, are naturally well formed: the front ones sharp, so that they may cut, the molars broad, so that they may grind. The canine teeth mark the boundary between the two, being of a nature intermediate between both — for what is in the middle shares in both extremes — and the canines are on one side sharp and on the other broad. It is the same too in the other animals, as many as do not have all their teeth sharp. And these teeth are especially of this kind and this number for the sake of speech; for the front teeth contribute much to the formation of the sounds of speech. [section 3] Some animals, as we said, have teeth only for the sake of food. But those that have them also for defense and for strength, some have tusks, as the pig does, others have sharp, interlocking teeth, for which reason they are called saw-toothed. For since their strength lies in their teeth, and this comes about through sharpness, the teeth useful for strength fall in alternately, so that they may not be blunted by rubbing against one another. [section 4] No animal is at once saw-toothed and tusked, because nature does nothing in vain and nothing superfluous; and in some animals the defense is by striking, in others by biting. That is why female pigs bite: they do not have tusks.
3| [section 5] But in general there is a point that ought to be grasped, one that will prove useful both here and in much of what will be said later. For nature assigns each of the organs of strength and defense to those creatures able to use it alone, or better than others, and most of all to whichever can use it best — for example a sting, a spur, horns, tusks, or anything of that kind. And since the male is stronger and more spirited, some animals have such parts only in the male, others have them more developed in the male. For as many parts as it is necessary for the females too to have, such as those for feeding, the females have them, but have them to a lesser degree; but as many as serve none of the necessities, they do not have at all. [section 6] And this is why, among deer, the males have horns but the females do not. The horns of female cattle also differ from those of bulls, and likewise among sheep. And of the males that have spurs, most of the females do not have them. [section 7]
4| It is the same too with the other such cases. All fish are saw-toothed except the one called the parrotfish; and many have teeth on their tongues as well, and on the roofs of their mouths. The reason for this is that, living in a liquid element, they necessarily take in the liquid along with the food, and must expel it quickly; for it is not possible for them to linger over grinding, since the liquid would then flow into the stomach. For this reason all of them are sharp-toothed for cutting. Again, their teeth are many and set in many places, so that, instead of grinding, they may cut the food into many pieces by sheer number. And they are voracious, because almost all their strength lies in these teeth. [section 8] Animals have the nature of mouth they have both for the sake of these functions and further for respiration, in the case of those animals that breathe and are cooled from outside. For nature itself, as we said, puts parts common to all creatures to use for many special purposes: so too with the mouth — food is common to all, but strength is peculiar to some, and speech to others, and further, breathing is not common to all.
5| [section 9] Nature has drawn these together into one part, producing a differentiation within this same part to match the differences of function. That is why some mouths are narrower, others large. For as many creatures as have mouths for the sake of food, breathing, and speech are narrower-mouthed, while of those that have them for the sake of defense, all the saw-toothed ones have mouths that open wide. For since their strength lies in their bites, it is useful for them that the mouth's gape be large; for they will bite more, and over a wider area, the more widely the mouth opens. And among fish too, the biting and carnivorous ones have a mouth of this kind, while the non-carnivorous ones have a tapering mouth; for that kind is useful to them, and the other useless. [section 10] For birds, the mouth is what is called the beak; for they have this instead of lips and teeth. This differs according to its uses and modes of defense. For the birds called hook-taloned, because they are carnivorous and feed on no fruit, all have a hooked beak; for this is useful for gripping, and, being naturally formed this way, is more forceful. [section 11] Their strength lies in this and in their talons; that is why they also have more hooked talons. For the rest, the beak is useful to each according to its way of life — for example, for woodpeckers it is strong and hard, and likewise for crows and ravens, while for small birds it is delicate, suited to gathering seeds and catching small creatures.
6| [section 12] As for the plant-eaters and those that live near marshes, such as the swimming birds and the web-footed ones, some have a beak useful in one way, while others among them are broad-beaked; for being of this shape, it can dig easily, just as the snout of the pig does among the quadrupeds — for the pig too is a root-eater. Further, the root-eating birds and those that live a similar life have the tips of their beaks notched in some cases; for this makes it easy for them, being plant-eaters. [section 13] Concerning the other parts in the head, then, an account has more or less been given. In humans, the part between the head and the neck is called the face, named, it seems, from its function; for because a human alone among animals stands upright, it alone looks forward, and it sends its voice forward as well. [section 1] We must now speak of horns; for these too grow naturally in the head, in those that have them. Nothing that is not viviparous has them. By resemblance and by transference of the word, the 'horns' of certain other things are also so called; but in none of these does the function of a horn actually belong to it. For it is for the sake of defense and strength that the viviparous animals have them, which does not hold for any of the other things said to have 'horns'; for none of these uses its 'horns' either to ward off attack or to overpower, which are the functions proper to strength.
7| [section 2] Now all the animals that are many-toed have no horn. The cause of this is that a horn serves as an aid to defense, while for the many-toed animals other aids are available: nature has given some of them claws, others teeth fit for fighting, and others some other part sufficient for defense. [section 3] Of the cloven-hoofed animals, most have horns for strength, and so do some of the solid-hoofed animals, and some have them for defense as well. But those to whom nature has not given some other means of defense for safety — such as speed of body, with which it has aided horses, or size, as with camels (for an excess of size is also enough to prevent destruction from other animals, which is what happens with camels, and still more with elephants) — these lack horns; and the tusked animals, such as the pig family, are cloven-hoofed. [section 4] Those for whom the outgrowth of horns is naturally useless, nature has furnished with a different aid instead: for example, in deer, speed (for their size and their being many-toed would harm them more than help them), and likewise in buffaloes and gazelles (for against some attackers they defend themselves by standing their ground with their horns, but from the more savage and stronger they flee); and in bonasi (for in these too the horns are naturally curved toward each other and useless) the discharge of excrement — for it is with this that the animal defends itself when frightened; and by this same discharge other animals too are saved. At the same time, nature has not given the same animals many sufficient means of defense together; and most of the horn-bearing animals are cloven-hoofed, though there is also said to be a solid-hoofed one, which they call the Indian ass.
8| [section 5] Now most animals — just as the body of animals that produce motion by means of it is divided into a right and a left — likewise naturally have two horns, for this same cause; but there are also single-horned animals, such as the oryx and the so-called Indian ass. The oryx is cloven-hoofed, while the ass is solid-hoofed. Single-horned animals have their horn in the middle of the head; for in this way each of the two parts would most fully have one horn, since the middle is equally common to both extremes. [section 6] It would seem reasonable that the solid-hoofed animal, rather than the cloven-hoofed, should be single-horned; for the hoof and the cloven hoof have the same nature as the horn, so that the same disposition occurs together in both the hooves and the horns. Further, the splitting and the cloven state are a deficiency of nature, so that it is reasonable that in the solid-hoofed animals, nature, having given the superiority in the hooves, removed it from above and made them single-horned. [section 7] And nature was right to place the growth of the horns upon the head, and not as Aesop's Momus finds fault with the bull for not having his horns on his shoulders, from which he would have made the blows strongest, but instead on the weakest
9| part of the head. For Momus did not see clearly when he found this fault. Just as if horns had grown somewhere else on the body, they would have provided weight without being of any use, and would in many cases have been an obstacle to the animal's activities — so too if they had grown on the shoulders. For one must consider not only from where the blows would be stronger, but also from where they would reach farther; so that, since these animals do not have hands, and having horns on the feet is impossible, and having them on the knees would have hindered the bending of the joint, it is necessary that they have them, as indeed they now do, upon the head. [section 8] At the same time, they are by nature least an obstacle to the other motions of the body when placed there. Horns are solid all the way through only in deer, and only deer shed them, being lightened of them for the sake of benefit, but of necessity because of their weight. In the other animals, the horns are hollow up to a point, and their tips are solid, because this is useful for delivering blows. And so that the hollow part too should not be weak, it is not made of skin alone; within it a solid core made of bone is fitted, for in this way the horns, while possessing what is most useful for strength, are also least troublesome for the rest of the animal's life.
10| [section 9] We have now said for what purpose horns exist by nature, and for what cause some animals have them of this kind and others do not; let us now explain how, while the necessary nature holds among the things that exist of necessity, the nature that operates according to reason makes use of them for some end. First, then, the bodily and earthy material is present in greater quantity in the larger animals, and we know of no horn-bearing animal that is altogether small; for the gazelle, the smallest of the known horn-bearers, is still not small in this sense. [section 10] One must study nature by looking at the many cases; for what is according to nature holds either universally or for the most part. Now the bony matter in the bodies of animals is earthy; hence, looking for the most part, one may say it is most abundant in the largest animals. [section 11] Accordingly, nature makes use, for aid and advantage, of the excess of residue of this bodily kind of matter that is present in the larger animals; and of what flows of necessity to the upper region, it allots some to teeth and tusks, and some to horns. This is why none of the horn-bearing animals has teeth in both jaws; for they lack the front teeth above — nature, having taken material from there, added it to the horns, and the nourishment that would have gone to these teeth is spent instead on the growth of the horns.
11| [section 12] As for why the female deer do not have horns, while having teeth like the males, the cause is that both sexes have the same nature, and it is a horn-bearing nature; but the horns have been taken away from the females because they would not be useful to the males either, and the females are less harmed by this lack because of their strength. In the other animals, in which such material is not diverted into horns, in some it has increased the size of the teeth generally in both sexes, and in others it has made tusks, like horns, out of the jaws. [section 1] Concerning the parts in the head, then, let this account stand; below the head, the neck grows in those animals that have a neck. For not all animals have this part, but only those that have the things for whose sake the neck exists; and these are the pharynx and what is called the esophagus. [section 2] The pharynx exists for the sake of breath; for through it animals draw in and send out breath, breathing in and breathing out. This is why those animals that do not have lungs also do not have a neck, such as the fish tribe. The esophagus is that through which food travels to the stomach.
12| So whatever animals have no neck also have no clearly distinguishable gullet. And there is no necessity for having a gullet for the sake of nourishment, since it does nothing to prepare the food. [section 3] 3 Further, it is possible for the stomach to be positioned right after the mouth, but it is not possible for the lung to be so positioned. For there must be some common channel, as it were, through which the breath is divided along the windpipe into the two branches, since the lung is two-lobed; and in this way it would carry out inhalation and exhalation most effectively. And since the organ concerned with breathing must of necessity have some length, it is necessary for the gullet to lie between the mouth and the stomach. Now the gullet is fleshy, but has a sinewy tension: sinewy, so that it can stretch as the food goes in; fleshy, so that it may be soft and yielding and not be damaged by being roughened by what passes down it. [section 4] 4 What is called the pharynx and windpipe is composed of cartilaginous substance, since it exists not only for breathing but also for voice, and what is going to produce sound must be smooth and have some firmness. The windpipe lies in front of the gullet, even though this gets in its way when it comes to receiving food; for if anything dry or wet slips into the windpipe, it produces choking, pain, and severe coughing fits. This is indeed something one might be surprised at in those who say that it is by this route that the animal takes in drink; for what has been described plainly happens to everyone into whom some of their food slips.
13| [section 5] 5 In many ways it appears absurd to say that it is by this route that animals take in drink. For there is no passage into the stomach from the lung, the way the gullet plainly runs from the mouth. Further, in vomiting and in nausea it is not unclear from where the fluid is seen to travel. [section 6] 6 It is also clear that the fluid is not collected straight into the bladder, but first into the stomach; for the residues of the stomach are visibly colored by the lees of dark wine, and this has often plainly happened also in cases of wounds to the stomach. But perhaps it is foolish to examine over-simple accounts too closely. [section 7] But the windpipe, 7 by being positioned as we said in front, is troubled by the food; but nature has contrived the epiglottis against this. Not all live-bearing animals have this, but only those that have a lung and hairy skin, and are not by nature scaly or feathered. In these, instead of the epiglottis, the pharynx itself contracts and opens, in the same way that in the others the epiglottis falls over and lifts back — lifting back for the entry and exit of breath, and folding down when food is going in, so that nothing may slip past into the windpipe. And if some fault occurs in this movement and someone draws breath while food is being carried in, this produces coughing and choking, as has been said.
14| [section 8] Both this movement and that of the tongue have been so 8 well contrived that, while the food is being smoothed in the mouth and passing right by it, it is chewed by the teeth only rarely, and only a small amount slips into the windpipe. [section 9] The animals mentioned do not have the 9 epiglottis because their flesh is dry and their skin is hard, so that such a part, if made of such flesh and such skin, would not be easily movable for them; instead, the contraction of the very extremity of the windpipe itself would occur more quickly than the contraction of an epiglottis made of flesh proper to it, such as the hairy animals have. This, then, is the reason why some animals have this part and others do not, and why nature has remedied the poor positioning of the windpipe by contriving what is called the epiglottis. [section 10]
15| 10 The pharynx of necessity lies in front of the gullet. For the heart lies in front and in the middle, and in it we say is the principle of life and of all motion and perception (for perception and motion belong to what is called the front; indeed it is by this very account that front and back are distinguished), while the lung lies where the heart is and around it, and breathing occurs both because of the lung and because of the principle present in the heart. Breathing occurs in animals through the windpipe; so since the heart must of necessity lie foremost among the front parts, the pharynx and windpipe must also of necessity lie in front of the gullet. For these lead toward the lung and the heart, while the gullet leads to the stomach. [section 11] 11 And in general, always, wherever nothing else greater stands in the way, the better and more honorable part is found among the upper rather than the lower, among the front rather than the back, and among the right rather than the left. [section 1]
16| 4 Concerning the neck, the gullet, and the windpipe, then, we have spoken; next in order is to speak about the internal organs. These belong properly to the blooded animals, and some blooded animals have all of them, others do not. None of the bloodless animals has an internal organ. Democritus seems not to have judged well about them, if indeed he thought that because of the smallness of the bloodless animals these organs are invisible in them. For as soon as the blooded animals form, even while entirely small, the heart and liver become visible; for in eggs, sometimes on the third day, these appear having the size of a mere point, and they are extremely small also in miscarried embryos. [section 2] 2 Further, just as not all the external parts have the same use for every animal, but each has been supplied its own, suited to its ways of life and its movements, so too the internal parts by nature differ from one animal to another. And the internal organs are proper to the blood-possessing animals, which is why each of them is composed out of blood-like matter. This is clear in their newborn young; for in these the organs are more blood-like and largest in proportion, because the form of the matter and its quantity are most conspicuous at the first formation. [section 3]
17| The heart, then, belongs to all the blooded animals; and the 3 reason for this has been stated before as well. For it is plain that the blooded animals must have blood; and since blood is fluid, there must be a vessel to contain it, and it is for this purpose that nature is evidently seen to have contrived the veins. And there must of necessity be one single origin of these; for wherever it is possible, one is better than many. And the heart is the origin of the veins. For they are plainly seen to come out of it and not merely to pass through it, and its own nature is vein-like, as being of the same kind. [section 4] Its position, too, occupies a ruling place: 4 for it lies about the middle, though rather toward the upper than the lower, and toward the front than the back; for in the more honorable parts nature has established the more honorable thing, wherever nothing greater prevents it. This is most evident in the case of human beings, but in the other animals too it tends, agreeably, to lie in the middle of the region required for life. The limit of this region is where the residues are excreted; but the limbs are formed differently in different animals, and are not among the things necessary for living, which is why animals live even when they are removed; and it is likewise clear that their addition does not destroy the animal. [section 5]
18| Those who say that the starting point of the blood vessels is in the head have not judged rightly. For first, they make many starting points, and scattered ones; and further, they place it in a cold region. This is shown by the head's being liable to chill, whereas the region around the heart is the opposite. [section 6] But as was said, the blood vessels pass through the other internal organs, but through the heart no blood vessel extends; hence it is clear too that the heart is a part and starting point of the blood vessels. And this is reasonable: the body of the heart is in the middle, and is naturally dense and hollow, and further full of blood, since the blood vessels take their origin from there — hollow so as to receive the blood, dense so as to guard the starting point of heat. For in the heart alone among the internal organs and among the parts of the body is there blood without blood vessels; in each of the other parts the blood is contained in the blood vessels. And this too is reasonable: the blood is channeled out of the heart into the blood vessels, but into the heart from nowhere else; for the heart is the starting point and source of the blood, or its first receptacle. [section 7]
19| This is made clearer still by dissections, and by the processes of generation: for the heart is the first of all the parts to become blooded as it forms. Further, the movements of pleasant and painful things, and in general of every act of perception, plainly begin from this point and are completed by reference to it. And this holds by reasoning too: there must be a single starting point, wherever that is possible. And the most naturally suited of positions is the middle; for the middle is one thing, and is equally or nearly equally accessible to everything. [section 8] Further, since nothing bloodless has perception, and blood itself has none, it is clear that whatever first possesses perception, possessing it as in a vessel, must be the starting point. And this appears to hold not only by reasoning but also by observation. For in embryos the heart is immediately seen moving among the parts, as if it were itself an animal, as being the starting point of nature for blooded creatures. Confirmation of what has been said is also the fact that it is present in all blooded animals; for they must necessarily have the starting point of the blood. [section 9] There is present
20| also the liver in all blooded animals; but no one would think it right to hold that it is the starting point either of the whole body or of the blood. For it is in no way situated in a position fitting a starting point, and, in the most precisely formed animals, it has the spleen set opposite it as a kind of counterweight. Further, it does not have within itself a receptacle for blood as the heart does, but like the rest of the parts, has its blood in a blood vessel. Further, a blood vessel extends through it, but none proceeds out of it; for the starting points of all the blood vessels are from the heart. [section 10] Since, then, one or the other of these must necessarily be the starting point, and the liver is not, the heart must necessarily be the starting point of the blood as well. For the animal is defined by perception, and the first thing capable of perception is the first blooded thing, and such is the heart; for it is both the starting point of the blood and the first blooded thing. [section 11] Its tip is sharp and firmer, and it is situated near the chest, and more toward the front of the body, so that it may not be chilled; for in all animals the chest is less fleshy, while the parts toward the back are fleshier, and so the heat has ample covering along the back. In the other animals the heart lies at the middle of the region of the chest, but in human beings it inclines slightly to the left, so as to offset the excessive chilling of the left side; for of all animals, the human being has the left side most chilled.
21| [section 12] That the heart is likewise situated in fish too has been said before, and also why it appears otherwise. Its point is turned toward the head, and this is the front, for the creature's motion is directed toward it. The heart also has a great quantity of sinews, and reasonably so; for the movements originate from it, and they are accomplished by pulling and relaxing, and this requires just such an instrument and strength. [section 13] The heart, as we have also said before, is naturally like a kind of animal in the creatures that possess it. It is without bone in all the animals we ourselves have observed, except horses and a certain kind of cattle; in these, because of their size, a bone underlies it, serving as a kind of support, just as in whole structures. [section 14] Of chambers, the hearts of the larger animals have three, those of the smaller have two, and all have at least one; the reason has been stated. For there must be some region of the heart serving as a receptacle for the first blood. That the blood comes to be first in the heart we have often said, on account of there being two governing blood vessels, the one called the great vessel and the aorta. Since each of these is a starting point of the blood vessels, and they have differences, which we shall discuss later, it is better that their starting points also be kept separate; and this would follow if the blood is twofold in nature and kept separate. This is why, wherever it is possible, there are two receptacles. It is possible in the large animals; for in these the hearts also have size.
22| [section 15] Further, it is better that there be three chambers, so that there may be one common starting point; for what is in the middle and extra is a starting point; and so a greater size is always needed for them, which is why only the largest hearts have three. [section 16] Of these, the right chamber has the most blood, and the hottest (which is why the right-hand parts of the body are also hotter), the left has the least and the coldest, and the middle chamber is in between in both quantity and heat. And it is the purest: for the starting point must be as much at rest as possible, and it would be such if the blood is pure, and in between in quantity and heat. [section 17] The hearts also have a certain articulation resembling seams. They are not joined together as though composed of several parts, but rather, as we have said, by articulation. They are more articulated in the more perceptive animals, and less articulated in the more sluggish ones, [section 18] as in the case of pigs. The differences among hearts, in respect of largeness and smallness
23| and hardness and softness, extend in some measure also to character. For the ones that lack perceptiveness have a hard and dense heart, while the perceptive ones have a softer one; and those with large hearts are cowardly, while those with smaller or middling hearts are bolder. For the affection that comes about through being afraid is already present in them beforehand, because the heat is not in proportion to the heart, and, being small within a large space, it is dimmed, and the blood becomes colder. Animals that have large hearts include the hare, the deer, the mouse, the hyena, the ass, the leopard, the weasel, and pretty much all the others that are manifestly cowardly, or vicious out of fear. [section 19] The same holds similarly also for the blood vessels and for the chambers: the large blood vessels and chambers are cold. For just as in a small room and a large one, an equal fire heats the larger room less, so it is with the heat in these too; for the blood vessel and the chamber are both vessels. [section 20] Further, extraneous movements chill each of the hot things, while in the more spacious vessels there is more air, and it has greater force; and this is why none of the animals with large chambers, nor any with large blood vessels, is fat in its flesh, but all or most of such animals appear to have inconspicuous blood vessels and small chambers,
24| [section 21] Of the internal organs, and of the parts in the body generally, the heart alone suffers no serious ailment — and reasonably so; for if the principle is destroyed, there is no source left from which help could come to the other parts that depend on it. A sign that the heart admits no ailment is that in none of the sacrificial victims has such an ailment ever been observed about it, as is observed in the case of the other organs. For the kidneys are often seen full of stones and tumors and boils, and so too the liver, and likewise the lung, and especially the spleen. [section 22] Many other affections, too, are seen occurring about these organs; least of all does the lung suffer about its windpipe, and the liver about its junction with the great vein, and reasonably so — for it is there that they most communicate with the heart. And in the case of animals that are observed dying of disease and such afflictions, when these are dissected, diseased conditions appear about the heart. [section 1] Concerning the heart, then — what sort of thing it is, and for what purpose and through what cause it belongs to the animals that have one — let so much have been said.
25| It would follow next to speak of the veins, both the great vein and the aorta; for these are the first to receive the blood from the heart, and the rest are offshoots of these. That they exist for the sake of the blood has been said before; for every fluid needs a vessel, and the class of veins is a vessel, and the blood is in these. Let us now say why there are two of them, and why, starting from a single principle, they extend throughout the whole body. [section 2] The cause of their converging on a single principle, and of their starting from one, is that every animal has, in actuality, a single sensitive soul, so that the part that possesses this primarily is also one — in the blooded animals both potentially and actually, in some of the bloodless animals only actually. This is why the principle of heat must also be in the same place; and this is the cause, for the blood too, of its fluidity and its heat. [section 3] So because the principle of perception and of heat is in a single part, the principle of the blood too is from one source; and because of the unity of the blood, the principle of the veins is also from one. There are two of them because the bodies of the blooded and locomotive animals are bipartite; for in all of these front and back, and right
26| and left, and up and down, are distinguished. [section 4] To the degree that the front is more honorable and more governing than the back, to that same degree the great vein exceeds the aorta; for the one lies among the parts in front, the other among those behind, and all the blooded animals have the former plainly visible, while the latter is in some faintly visible and in some not visible at all. The reason the veins are distributed throughout the whole body is that blood is the matter of the whole body — and for the bloodless animals, the analogous fluid — and this lies in the vein, or in what is analogous to a vein. [section 5] How animals are nourished, and from what, and in what way they take up nourishment from the stomach — it is more fitting to examine and discuss this in the discourses on generation. But since, as we have said, the parts are composed out of the blood, it is reasonable that the flow of the veins should by nature extend through the whole body; for the blood too must be present throughout and alongside every part, if indeed each of the parts is composed out of it. [section 6] It is much as in gardens: water-channels are laid out from a single source and spring into many conduits, and further ones again, so as to distribute water everywhere; and in buildings, stones are laid along the whole outline of the foundations, since garden-plants grow from water, while foundations are built up out of stones — in the same way nature too has channeled the blood throughout the whole body, since this by nature is the matter of every part.
27| [section 7] This becomes evident in the parts most thinned out; for nothing else is visible besides the veins — just as with vine leaves and fig leaves, and other such things; for when these too dry up, only their veins are left. [section 8] The reason for this is that blood, and what is analogous to it, is potentially body — is potentially flesh, or what is analogous to flesh. So just as, in irrigation systems, the largest of the trenches remain, while the smallest ones are the first and quickest to be obscured by silt, and become visible again once the silt is cleared out, in the same way, of the veins, the largest remain, while the smallest become flesh in actuality, though they are no less veins potentially. This is why, wherever the flesh is intact, blood flows out when it is cut, even though there is no such thing as blood without a vein — yet no small vein is apparent, just as in the irrigation channels the trenches are not apparent until the silt is removed. [section 9] The veins always proceed from larger to smaller, until the passages become smaller than the thickness of the blood; through these there is no passage for blood, but there is for the residue of the moist fluid which we call sweat — and this occurs once the body has been heated through and the small veins have opened up.
28| [section 10] In fact it has already happened to some people to sweat a blood-like residue, on account of a bad bodily condition: the body having become porous and loose, and the blood having become over-liquid through poor concoction, because the heat in the small veins was too weak, from its scantiness, to concoct it. For it has been said that everything that is a compound of earth and water thickens when concocted, and nourishment and blood are a mixture of both. Heat proves unable to concoct not only through its own scantiness but also through the quantity and excess of the nourishment brought in — for it is weak relative to only a little. And the excess is of two kinds, in quantity and in quality; for not everything is equally easy to concoct. [section 11] Blood flows most readily through the widest of the passages; this is why painless flows of blood occur from the nostrils, the gums, and the anus, and sometimes also from the mouth, and not, as from the artery, with violence. [section 12] The great vein and the aorta, though separate above, cross over below and hold the body together. For as they proceed they split according to the two-fold branching of the limbs, and the one goes from the front to the back, the other from the back to the front, and they meet into one; for just as, in woven things, greater continuity results, so too through this crossing-over of the veins the front parts of the body are bound together with the back. And the same thing happens likewise from the heart in the upper regions.
29| [section 13] How the veins stand to one another in precise detail must be studied both from dissections and from the History of Animals. Let this suffice concerning the veins and the heart; the other internal organs must be examined by the same method. [section 1] Animals have a lung, then, because one class of animals is land-dwelling.. For it is necessary that cooling occur for the heat, and the blooded animals need this cooling from outside, since they are hotter; the bloodless animals, on the other hand, are able to cool themselves by means of their connate breath as well. Cooling from outside must be done either by water or by air. This is why none of the fish has a lung, but gills instead, as has been said in the treatise on respiration; for they achieve their cooling by water, while the animals that breathe do so by air, and this is why all the animals that breathe have a lung. [section 2] All the land animals breathe, and so do some of the water animals, such as the whale and the dolphin and all the cetaceans that spout. For many animals share in both natures: some of the land animals that take in air, on account of the blend of their bodies, spend most of their time in water; and some of the water animals share so much in the land-dwelling nature that the end of their life depends on breath.
30| [section 3] The lung is the organ of breathing; it has the origin of its motion from the heart, but it provides room for the entry of breath through its own sponginess and size. For when it rises, the breath flows in, and when it contracts, the breath goes out again. [section 4] The claim that the lung exists for the sake of the heart's leaping has not been well stated. For the leaping occurs, so to speak, only in man, because only man experiences hope and expectation of the future; and in most animals the heart lies far off and is positioned higher up than the lung, so that the lung contributes nothing to the leaping of the heart. [section 5]
31| The lung differs greatly among animals. Some have it full of blood and large, others smaller and spongy: the live-bearing animals have it larger and full of blood because of the heat of their nature, while the egg-laying animals have it dry and small. It is capable of expanding greatly when inflated with breath, as in the four-footed but egg-laying land animals, such as lizards and tortoises and every such kind, and further, in addition to these, in the nature of the winged creatures, the so-called birds. For in all of these the lung is spongy and like foam; for just as foam collapses from a large mass into something small when compressed, so the lung of these creatures is small and membrane-like. That is why all these animals are without thirst and drink little, and can hold out a long time in water; for since they have only a little heat, they are sufficiently cooled for a long time by the very motion of the lung, which is airy and empty. [section 6] It also happens that the bodies of these animals are, generally speaking, smaller; for heat promotes growth, and abundance of blood is a sign of heat. Further, heat makes bodies more upright, which is why man is the most upright of all animals, and the live-bearing animals more upright than
32| the other four-footed animals; for none of the live-bearing animals burrows into holes the way the egg-laying ones do, whether footless or ground-walking. [section 7] In general, then, the lung exists for the sake of breathing, and its being bloodless and of this spongy kind exists for the sake of a certain class of animals; but the common name for these has none, unlike 'bird,' which has been given as a name for a particular class. That is why, just as being a bird derives from something, so too, for those animals, having a lung of this kind belongs to their substance. [section 1] Among the viscera, some seem to be single in nature, such as the heart and the lung, others double, such as the kidneys, while about others it is disputed which way they stand. For the liver and the spleen would appear to fall under both descriptions: each seems single, yet also seems, as it were, to be two organs of similar nature standing in place of one. In fact, all of them are double. [section 2] The cause is that the extension of the body, while itself twofold, contributes to a single principle: one dimension is up and down, another is front and back, and another is right and left. That is why the brain, too, tends to be two-parted in all animals, and likewise each of the sense organs. By the same reasoning the heart is two-parted in its chambers. And the lung in egg-laying animals is separated to such a degree that they seem to have two lungs. As for the kidneys, their doubleness is plain to anyone.
33| [section 3] But concerning the liver and the spleen, one might rightly be puzzled. The reason is that in animals which have a spleen of necessity, the spleen would seem to be a kind of bastard liver, while in those that do not have one of necessity, but only a very tiny one, as it were for the sake of a mark, the liver is clearly two-parted: the larger part tends to be positioned on the right, the smaller on the left. [section 4] Nonetheless, in the egg-laying animals this is less evident, though in some of them, as also in certain live-bearing animals, it is conspicuously separated: for instance, in some regions hares are held to have two livers, as is also true of certain fish, particularly the cartilaginous ones. And it is because the liver's position lies rather on the right that the nature of the spleen has come to exist, so that it is necessary in a way, but not to an excessive degree, in all animals. [section 5] The cause, then, of the viscera being double in nature is, as we have said, that right and left are two; for each of the two sides seeks its like, just as they themselves tend to have a similar and twin nature — just as right and left are twin yet joined together into one, so likewise is each of the viscera.
34| [section 6] The viscera below the diaphragm all exist, in common, for the sake of the veins, so that these, being suspended aloft, remain in place through their attachment to the body. For they are cast toward the body like anchors, by means of parts extended from them: from the great vein toward the liver and the spleen. For the nature of these viscera takes hold of it like nails fastening it to the body — the liver and the spleen fastening the great vein toward the sides of the body (for from this vein alone do veins stretch to them), and the kidneys fastening it toward the back. And to the kidneys a vein stretches on each side, not only from the great vein but also from the aorta. [section 7] These things, then, come about through these organs for the constitution of animals: the liver and the spleen assist in the concoction of nourishment (for, being full of blood, they have a hot nature), while the kidneys assist with the residue that is secreted into the bladder. [section 8] The heart and the liver, then, are necessary to all animals: the heart because of the principle of heat (for there must be something like a hearth in which the kindling principle of nature is set, and this must be well guarded, like
35| an acropolis of the body), and the liver for the sake of concoction. All blooded animals need these two, which is why all blooded animals have only these two viscera; and those that breathe have a third, the lung. [section 9] The spleen belongs to those animals that have it by accidental necessity, just like the residues — both the one in the stomach and the one around the bladder. That is why in some animals it is deficient in size, as in some of the winged creatures that have a hot stomach, such as the dove, the hawk, and the kite, and likewise among the egg-laying four-footed animals (for they have one that is altogether small), and in many of the scaly animals; these last also lack a bladder, because their residue passes through their porous flesh into feathers and scales. For the spleen draws off from the stomach the residual moisture, and, being full of blood, is able to help concoct it. [section 10] If the residue is too abundant, or the spleen too lacking in heat, animals become diseased, being full of nourishment; and because of the backflow of moisture that occurs there, in many animals the stomachs become hard as they grow spleen-diseased, as happens to those that urinate excessively, on account of the moisture being drawn back and forth. But in those animals in which little residue is produced, as in birds and fish, some have a spleen that is not large, and others have one merely as a token.
36| [section 11] And in the four-footed egg-laying animals too the spleen is small and firm and kidney-like, because the lung is spongy and they drink little, and the residue that is left over turns into their body and into their scales, just as in birds it turns into feathers. But in those that have a bladder and a blooded lung, the spleen is moist, both for the reason stated and because the nature of the left parts as a whole is more moist and more cold. For each of the opposites is arranged with its kindred column: right is opposite to left, and hot is opposite to cold, and these belong to the same column as one another in the way stated. [section 12] The kidneys do not belong to the animals that have them of necessity, but for the sake of the well and the fine; for they exist, by their own proper nature, for the sake of the residue that collects in the bladder, in those animals in which a greater amount of such sediment occurs, so that the bladder may perform its own function better. [section 13] Since it turns out that animals have both the kidneys and the bladder for the sake of the same use, we must now speak about the bladder, passing over the next part in the order of number; for nothing has yet been determined about the diaphragm, and this is one of the parts concerning the viscera.
37| [section 1] Not all animals have a bladder; rather nature appears to intend to give it to those that have a blooded lung only, and reasonably so in their case. For because of the superiority of nature that they possess in this part, these are the animals most given to thirst, and they need not only dry food but a greater amount of moist food as well, so that of necessity a greater residue also comes about, and not so much only as is concocted by the stomach and excreted along with its residue. There must therefore be something receptive of this residue as well. [section 2] This is why all that have a lung of this kind have a bladder; but those that do not have such a lung, but either drink little because their lung is spongy, or take in moisture as a whole not for the sake of drinking but for the sake of food — as insects and fishes do — and further those that are feathered or covered with scales or with horny plates, these, because of the small amount of moisture they take in and because the residue that is left over turns into these parts, none of them has a bladder, except the tortoises
38| among the horny-plated animals. And here too nature has been stunted only in this respect. The reason is that the sea tortoises have a fleshy, blooded lung, similar to that of the ox, while the land tortoises have one larger than is proportionate. Further, because what encloses it is shell-like and dense, and the moisture does not transpire through porous flesh as it does in birds and snakes and the other horny-plated animals, so much sediment comes about that their nature needs to have some part that is receptive and vessel-like. So among such animals only these have a bladder for this reason — the sea tortoise a large one, the land tortoises a quite small one. [section 1] The case is similar too with the kidneys. For none of the feathered animals nor of the scaly ones nor of the horny-plated ones has kidneys either, except the sea tortoises and the land tortoises; but it is as though the flesh assigned to kidneys, instead of occupying a distinct region, is dispersed into many parts. Flat kidney-like structures occur in some birds. The land-tortoise called the emys has neither bladder nor kidneys; for because of the softness of its shell the moisture readily transpires. [section 2] So the emys, for this reason, has neither of these parts; but all the other animals that have a blooded lung, as has been said, turn out to have kidneys. For nature makes use of them at once for the sake of the veins and for the excretion of the moist residue; for a passage leads into them from the great vein.
39| [section 3] All kidneys have a hollow, greater or smaller, except those of the seal; these, being like those of the ox, are the most solid of all, and those of man are also like those of the ox; for they are as it were composed of many small kidneys and are not uniform, like those of sheep and the other four-footed animals. This is why the ailment of the kidneys is hard for men to shake off once they have fallen ill of it; for it turns out that, since as it were many kidneys are diseased, the cure is more difficult than for those in whom only one is diseased. [section 4] The passage that stretches from the vein does not terminate in the hollow of the kidneys, but is used up into the body of the kidneys; this is why no blood forms in their hollows, nor does it congeal there in the end. [section 5] From the hollow of the kidneys two vigorous bloodless passages lead to the bladder, one from each kidney, and other strong and continuous ones from the aorta. These are arranged in this way so that the residue of moisture may travel from the vein into the kidneys, while the sediment that forms from the moisture as it filters through the body of the kidneys flows together into the middle — the hollow which most of them have — for which reason this is the most foul-smelling of the viscera. And from the middle, through these passages, it is then secreted into the bladder, now rather as residue.
40| [section 6] The bladder is moored from the kidneys; for, as has been said, strong passages stretch toward it. The kidneys, then, exist for these reasons, and have the capacities stated. In all animals that have kidneys, the right one is higher than the left; for because motion is from the right, and because of this the nature of the right parts is stronger, it is necessary that, for the sake of motion, all the parts should be led further forward toward the upper region — since indeed animals also raise the right eyebrow more, and hold it more arched than the left. [section 7] And because the right kidney is drawn up higher, the liver touches the right kidney in all animals; for the liver is on the right side. The kidneys have more fat than any of the other viscera, of necessity because the residue is filtered through the kidneys; for the blood that is left behind, being pure, is well concocted, and the end product of blood's good concoction is fat and suet. For just as in things that have been burned dry, such as ash, some fire is left behind, so too in things that have been concocted while moist; for some portion of the heat that has done the work is left behind. This is why what is fatty is light and floats on top in liquids.
41| [section 8] This does not happen within the kidneys themselves, because the organ is dense, but it collects on the outside — fat in animals of the fatty kind, suet in those of the suety kind; the difference between these has been stated earlier elsewhere. [section 9] So they become fatty of necessity, for this reason, from what happens of necessity to animals that have kidneys; but they become so for the sake of preservation as well, and because the nature of the kidneys is hot. For being at the extremity they need more warmth; for the back is fleshy, so as to be a bulwark for the viscera around the heart, while the loin is fleshless (for the bending parts of all animals are fleshless); so instead of flesh, fat becomes a bulwark for the kidneys. [section 10] Further, being fat, they separate out and concoct the moisture better; for what is fatty is hot, and heat concocts. For these reasons, then, the kidneys are fatty, and in all animals the right one is less fatty. The reason is that the nature of the right parts is dry and more given to motion; and motion is opposed to this — for it melts what is fat all the more.
42| [section 11] For the other animals, then, it is advantageous to have fat kidneys, and often they have them entirely filled with fat; but the sheep, when this happens to it, dies. Even if sheep are very fat, still something is lacking, if not in both kidneys, then in the right one. The cause of this happening especially among sheep is that in animals with soft, tallow-like fat the fat is liquid, so that the pneumata shut in within it do not, in the same way, cause the pain. [section 12] This is the cause of the mortification; and this is why, among human beings too, for those whose kidneys are diseased, although becoming fat is beneficial, still, if they become excessively fat, fatal pains result. In the other animals with suet-fat, the suet is less dense than it is in sheep. And sheep far exceed the other animals in quantity of fat; for sheep develop fat around the kidneys faster than any other animal. [section 13] So when the moisture and the pneumata are shut in on account of the mortification, sheep are killed quickly; for through the aorta and the great vein the affection reaches the heart at once, and the passages from these veins are continuous with the kidneys. We have now spoken about the heart and the lung, and about the liver, the spleen, and the kidneys.
43| [section 1] These parts happen to be separated from one another by the partition. This partition some people call the phrenes; it marks off the lung and the heart from what lies below. This partition, in blooded animals, is called, as has already been said, the phrenes. All blooded animals have it, just as they have a heart and a liver. [section 2] The cause of this is that it exists for the sake of marking off the region around the stomach from the region around the heart, so that the principle of the perceptive soul may be unaffected and not be quickly overtaken by the exhalation that arises from food and by the quantity of imported heat. For nature made this division with just this end in view, constructing the phrenes as a kind of adjoining wall and barrier, and separated the more honorable from the less honorable, in all the cases where it is possible to separate an upper region from a lower one; for the upper region is that for the sake of which the rest exists, and is the better one, while the lower is that which exists for the sake of the upper and is necessary — the part that receives food. [section 3] The partition is fleshier and stronger toward the ribs, but more membranous in the middle; for arranged this way it is more useful for strength and for tension. That the phrenes are, so to speak, an offshoot with respect to the heat coming from below is shown by a sign drawn from what actually happens: whenever, on account of their proximity, they draw in hot and residual moisture, this immediately and visibly disturbs thought and perception — which is why they are called phrenes, as if they shared to some degree in thinking.
44| [section 4] The phrenes themselves share in nothing of thought, but being close to the parts that do share in it, they make the change in thought evident. This is also why they are thin in the middle — not only of necessity, because, being fleshy, the parts toward the ribs must be fleshier, but so that they may share in as little moisture as possible; for if they were fleshy there too, they would both hold and draw in a great deal more moisture. [section 5] That when heated they quickly make the effect on perception evident is shown also by what happens in the case of laughter. For people who are tickled laugh quickly, because the motion arrives quickly at this region. The phrenes are heated only gently, yet even so they make the effect evident and set thought in motion against one's own choice. [section 6] The cause of man alone being susceptible to tickling is both the thinness of his skin and the fact that man alone among animals laughs. Tickling is laughter produced by this kind of scratching of the region around the armpit. [section 7] They say that laughter also occurs from blows received in war, when the blow lands in the region around the phrenes, on account of the heat produced by the blow. This is a claim more worth trusting from those who report it than the one about the head — that a man's head speaks after being cut off. For some people say this, bringing in Homer as well, claiming that this is why he composed the line (Iliad 10.457; Odyssey 22.329): 'φθεγγομένη δ' ἄρα τοῦ γε κάρη κονίῃσιν ἐμίχθη' (and his head, speaking, mingled at once with the dust) — using 'φθεγγομένη' (speaking, as though the head itself spoke), not 'φθεγγομένου' (speaking, as though he himself was still speaking).
45| [section 9] In Caria they believed a thing of this sort so firmly that they even held a trial over one of the local people because of it. For when the priest of Zeus Hoplosmios died, and it was unclear at whose hand, some people claimed to have heard the severed head repeatedly saying, over the dead man, 'Kerkidas killed him'; and so, searching for the person in the district whose name was Kerkidas, they convicted him. [section 10] But it is impossible to speak once the windpipe has been severed and without the motion that comes from the lung. Among the barbarians, too, among whom heads are cut off quickly, nothing of this sort has ever occurred. Further, for what reason does it not occur in the other animals? The case of laughter, when the phrenes are struck, is reasonable enough — for none of the other animals laughs. But that the body should move forward some distance once the head has been removed is not at all unreasonable, since even bloodless animals go on living for a long time afterward; the cause of this has been explained elsewhere. [section 1] We have now stated, then, for the sake of what each of the viscera exists; and each has come to be of necessity at the internal ends of the veins. For it is necessary that moisture come out there, and that this moisture be blood-like, and that from it, as it combines and solidifies, the body of the viscera is formed. This is why they are blood-like, and have a bodily nature similar to blood itself, but unlike that of the other parts. All the viscera are enclosed in a membrane; for a protective covering is needed
46| to keep them unaffected, and one that is light. The membrane is by nature just such a thing: dense enough to keep things off, without flesh so that it neither draws in nor holds moisture, and thin so that it may be light and add no weight. [section 2] The largest and strongest of the membranes are those around the heart and around the brain, and reasonably so; for these organs need the most protection, since protection is for the governing parts, and these are the parts most governing of life. [section 1] Some animals have the full number of these organs, others do not have all of them; which animals these are, and for what cause, has been stated earlier. And even among those that have them, they differ from one another: for not all animals that have a heart have hearts of a similar kind, nor, one might say, do they have any of the other viscera alike either. The liver, for instance, is many-lobed in some, more single in growth in others — this is so first of all among the blooded, live-bearing animals themselves; and the livers of fish and of the four-footed egg-layers differ still more, both from these and from one another.
47| [section 2] The liver of birds is most similar to that of the live-bearing animals; for its color is clean and blood-like, just as in those animals. The cause is that the bodies of birds are extremely well-aerated and do not carry much base residue. This is also why some live-bearing animals lack gall-bladders: the liver contributes a great deal toward the good blending and health of the body, since for these animals their end lies chiefly in the blood, and the liver is the most blood-like of the viscera after the heart. [section 3] The livers of most four-footed egg-layers and of fish are somewhat pale, and in some cases entirely poor, just as their bodies too happen to be of a poor temperament — the toad's and the tortoise's, for example, and those of other such animals. [section 4] Horned, cloven-hoofed animals have a round spleen, like the goat, the sheep, and each of the others, unless one grows more elongated in length on account of its size, as happens with the spleen of the ox. All the many-toed animals have an elongated spleen, like the pig, man, and the dog, while the single-hoofed animals are intermediate between these two and mixed in form — broad in one part and narrow in another — as with the horse, the mule, and the donkey.
48| 13 The viscera differ from flesh not only in the bulk of the body but also in that the one has an outer position and the other an inner one. The reason is that their nature is connected with the veins: some of them exist for the sake of the veins, others cannot exist without veins. [section 1] 14 Beneath the diaphragm lies the stomach, in animals that have a gullet, where this part terminates; in those that have none, it lies right at the mouth. Adjoining the stomach is what is called the intestine. [section 2] 2 The reason each of these parts belongs to the animals that have them is clear to everyone. For the food that has entered must be received, and the residue, once its moisture has been drawn off, must be sent out, and the place of the undigested food must not be the same as that of the residue, and there must also be some place in which the food undergoes change. For one part will hold the food that has entered, another the useless residue; and since the time proper to each of these is different, it is necessary that they be separated by place as well. [section 3] 3 But the fuller determination of these matters belongs more properly to the discussions of generation and nutrition; here we must examine the differentiation of the stomach and of the parts that work with it.
49| [section 4] 4 For animals do not resemble one another either in the size or in the forms of these parts. Among the blooded, live-bearing animals, those that have teeth in both jaws have a single stomach — for example man, dog, lion, and the rest that are many-toed, and those that are single-hoofed, such as horse, mule, donkey, and those that are cloven-hoofed but have teeth in both jaws, such as the pig — except that where the size of the body and the character of the food require it (the food not being easy to digest but thorny and woody), the animal has more than one stomach, as does the camel, like the horned animals. For the horned animals do not have teeth in both jaws; and it is for this reason that the camel too, having no horns, is not among those with teeth in both jaws, because it is more necessary for it to have this kind of stomach than to have front teeth. So, since it has a stomach like that of animals without teeth in both jaws, its dental arrangement is likewise similar to theirs, as though the teeth were of no further use to it. [section 5] 5 At the same time, since its food is thorny, and the tongue must be fleshy, nature has made use of the earthy material from the teeth to counter the hardness of the palate. [section 6]
50| The camel also chews the cud, like the horned animals, 6 because it has stomachs similar to those of the horned animals. Each of these has several stomachs — for example sheep, ox, goat, deer, and the other such animals — so that, since the mouth falls short in its work upon the food because of the deficiency of teeth, the several stomachs, receiving the food one from another, may compensate: the one receiving it unworked, another working it more, another completely, and another making it smooth. This is why such animals have more places and parts of this kind. [section 7] These are called the stomach, the honeycomb-bag, 7 the many-plies, and the reed. The manner in which these stand to one another in position and in form must be studied from the History of Animals and from dissections. [section 8] For the same reason the class of birds also has a differentiation in the part that receives food. 8 For since birds too do not perform the work of the mouth at all (they are toothless) and have nothing with which to divide or grind the food,
51| for this reason some have, before the stomach, what is called the crop, in place of the working of the mouth; others have a broad gullet, or, before the stomach, some bulging part of it in which they store up the unworked food in advance; or some elevated part of the stomach itself; others have the stomach itself strong and fleshy, so as to be able to store the food a long time and to concoct it even unground; for by its power and by the heat of the stomach, nature makes up for the deficiency of the mouth. [section 9] 9 There are some that have none of these, but instead a long crop — those that are long-legged and live by marshes — because of the wetness of their food. The reason is that for all these the food is easy to grind, so that it follows that the stomachs of such birds are moist, on account of both the lack of concoction and the nature of the food. [section 10] 10 The class of fishes has teeth, and these, in almost all of them one may say, are jagged; for it is a small class that does not have teeth of this kind, such as the one called the parrotfish, which is also reasonably thought to chew the cud, and for this reason alone; for even animals without teeth in both jaws but with horns chew the cud.
52| [section 11] 11 All fish have sharp teeth, so that they are able to divide their food, but divide it poorly; for they cannot linger over it and take time. This is also why they do not have broad teeth, nor is it possible for them to grind; such teeth would have been useless to them. Further, some have no gullet at all, others a short one. But to assist digestion, some have stomachs like those of birds, and fleshy, such as the grey mullet, while most have, alongside the stomach, dense outgrowths, so that in these, as in little storage-pits, they may store the food and let it putrefy somewhat and concoct it. [section 12] 12 Fish have their outgrowths in the opposite position to birds; for in fish they are up near the stomach, while in the birds that have such outgrowths they are down near the end of the intestine. Some of the live-bearing animals also have intestinal outgrowths lower down, for the same reason. [section 13] The whole class of fishes, because their work upon the food is deficient, 13 so that they pass it out undigested, is gluttonous for food, as are all the other animals that have a straight intestine; for since the passing-out happens quickly, and because of this the enjoyment is brief, the appetite must also quickly recur.
53| [section 14] It has been said earlier that the animals with teeth in both jaws 14 have a small stomach; and nearly all of these fall into two differentiations: some have a stomach like that of the dog, others like that of the pig. The pig's stomach is larger and has certain moderate folds so that digestion may take longer, while the dog's is small in size and is much exceeded by the length of the intestine, and smooth within. For after the stomach, the nature of the intestines is present in all animals. [section 15] This part too, like the stomach, exhibits many differences. 15 In some it is simple and uniform when unwound; in others it is not uniform: in some the part near the stomach is wider and that near the end narrower (which is why dogs pass this kind of residue with effort), while in the majority it is narrower above and wider near the end. [section 16] The intestines of the horned animals are larger and have many convolutions, 16 and in these the bulk of the stomach and of the intestines is also greater, on account of their size; for practically all the horned animals are large, because of the working their food requires.
54| [section 17] In all animals that do not have a straight intestine, this part becomes wider as it proceeds, and they have what is called the colon, and a blind and bulky part of the intestine, and then after this again something narrower and coiled. What comes after this stretches straight toward the exit for the residue, and in some animals this part, the so-called rectum, is fatty, in others it is without fat. [section 18] All these things have been contrived by nature for the tasks suited to nutrition and to the residue that is produced. For as the residue proceeds and descends, wide space is provided, useful also for undergoing change, in animals that digest their food more easily and need more food, because of the size or the heat of these regions. Then again from here, just as a narrower intestine receives the food from the upper stomach, so from the colon and the wide space in the lower stomach the residue again comes into something narrower, into the coil, thoroughly dried out, so that nature may store it up and the discharge of the residue not happen all at once. [section 19] So then, whatever animals need to be more temperate with regard to the taking of food do not have great wide spaces in the lower stomach, but have more coils and are not straight-gutted. For wide space produces desire for quantity, while straightness produces speed of desire; and so, of animals, those that have simple or wide receptacles are gluttonous for quantity, and those with straight guts are gluttonous for speed.
55| [section 20] Since in the upper stomach, at the first entry of the food, the food must be fresh, while as it proceeds downward it is dung-like and dried out, there must also be something in between, in which it undergoes change and is neither still fresh nor yet dung. For this reason all such animals have what is called the jejunum, in the thin intestine that comes after the stomach; for this lies between the upper part, in which the food is undigested, and the lower part, in which the residue is already useless. [section 21] This occurs in all animals, but it is conspicuous in the larger ones, and in those that have fasted but not yet eaten; for then it becomes a boundary-region between both places, whereas in animals that have eaten the moment of transition is brief. In females, then, the jejunum occurs wherever it happens to fall in the upper intestine; the males have it before the blind gut and the lower stomach. [section 1] Chapter 15. All the many-stomached animals have what is called rennet, and among the single-stomached animals, the hare alone has it. Of the many-stomached animals that have rennet, it is found neither in the great paunch nor in the honeycomb bag nor in the last stomach, the reed, but in the part between the last stomach and the first two, in what is called the manyplies.