Aristotle · a new plain-English translation from the original language
1| B. [section 1] Out of which parts, then, and how many, each of the animals is composed has been shown more precisely in the Researches concerning them; but the causes on account of which each is disposed in this way we must now examine, separating this inquiry, in its own right, from what was said in the Researches. There being three kinds of composition, one would place first the composition out of what some call the elements, such as earth, air, water, fire. But it is perhaps better to speak in terms of the powers, and not all of these, but as has been said before elsewhere. For the moist and the dry and the hot and the cold are the matter of composite bodies; the other differentiae follow upon these — weight and lightness, density and rarity, roughness and smoothness, and the other such affections of bodies. The second composition, built out of the first, is the nature of the uniform parts found in animals, such as bone and flesh and the other things of that kind; and the third and last in number is that of the non-uniform parts, such as face and hand and parts of that sort. [section 2]
2| Since the order is reversed as between coming-to-be and substance — for what is later in coming-to-be is prior in nature, and what is last in coming-to-be is first (for a house does not exist for the sake of bricks and stones, but these for the sake of the house; and the same holds for the other matter as well); and it is clear not only by induction that this is how the matter stands, but also on rational grounds. For everything that comes to be, comes to be out of something and toward something, and proceeds from a starting-point to a starting-point, from the first thing that moves it and already possesses a certain nature, toward some shape or some other such end — for man begets man, and plant begets plant, out of the matter underlying each. In time, then, the matter and the coming-to-be must be prior; but in account, the substance and the shape of each thing are prior. This is clear if one states the account of the coming-to-be: for the account of the building includes the account of the house, but the account of the house does not include the account of the building. [section 3]
3| And the same holds likewise for the other cases too. So the matter of the elements must exist for the sake of the uniform parts. For these are later than those in coming-to-be, and the non-uniform parts are later still than these; for these already have their end and their limit, having reached the composition belonging to the third number, just as in many cases it happens that processes of coming-to-be are completed at a third stage. Animals, then, are composed of both kinds of these parts, but the uniform parts exist for the sake of the non-uniform; for it is the non-uniform parts that have functions and actions — for instance the eye, the nostril, the whole face, the finger, the hand, and the whole arm. And since the actions and motions belonging to animals, both as wholes and in parts of this sort, are of many different kinds, it is necessary that the things they are composed of have unlike capacities: for some purposes softness is useful, for others hardness, and some parts need to be capable of tension, others of bending. [section 4] Now the uniform parts have these capacities distributed part by part (for one of them is soft, another hard; one moist, another dry; one viscous, another brittle), while the non-uniform parts have them in many combinations put together with one another; for a different capacity is useful for pressing with the hand and for grasping. That is why the organic parts are composed out of bones and sinews
4| and flesh and the other things of that kind — and not the uniform parts out of the non-uniform. [section 5] As for how, then, the matter stands as stated for the sake of something, on account of this cause; but since it is also asked how it is necessary for things to be so, it is clear that they existed beforehand standing toward one another of necessity in this way. For the non-uniform parts can be composed out of the uniform, either out of several or out of one, as is the case with some of the internal organs; for these are varied in shape while being, so to speak, simply of uniform composition. [section 6]
5| But it is impossible for the uniform parts to come from these non-uniform parts; for a uniform part would then be many non-uniform ones. So it is for these reasons that some of the parts in animals are simple and uniform, while others are composite and non-uniform. And since there are, among animals, both instrumental parts and organs of sense, each of the instrumental parts is non-uniform, as I said before, while perception occurs in all cases in the uniform parts, because each kind of perception belongs to some one genus, and the organ of each sense must be receptive of the objects perceptible by that sense. Now what is potentially something is acted on by what is actually that thing, so that the agent and the patient are the same in genus, each being one; and this is why none of the natural philosophers attempts to say that a hand or a face or any such part is earth in one portion, water in another, and fire in another, while they do link each of the organs of sense to one of the elements, saying that one is air, another fire. Since perception occurs in the simple parts, it is reasonable that touch above all should occur in an organ of sense that is uniform, yet least simple of the sense organs; for this sense seems above all to belong to more than one genus, and to have many contrarieties. [section 7]
6| What is perceptible to touch is what is hot, cold, dry, wet, and anything else of that sort; and the organ of these, flesh, or what is analogous to it, is the most bodily of the sense organs. Since it is impossible for an animal to exist without perception, it would for this reason be necessary for animals to have some uniform parts; for perception resides in these, while their actions come about through the non-uniform parts. [section 8] Since the perceptive capacity, the capacity that moves the animal, and the nutritive capacity all reside in the same part of the body, as has been said elsewhere before, it is necessary that the part which first possesses these principles be, insofar as it is receptive of all the objects of perception, one of the simple parts, but insofar as it produces motion and action, one of the non-uniform parts. This is why, in bloodless animals, the analogous part, and in blooded animals, the heart, is of this kind; for it divides into uniform parts, as does each of the other viscera, yet because of the shape of its form it is non-uniform. And each of the other so-called viscera has followed the same pattern; for they are all composed of the same matter, since the nature of all of them is bloodlike, because they are situated at the outlets and junctions of the blood vessels.
7| [section 9] Just as mud settles from flowing water, so the other viscera are, as it were, deposits from the flow of blood through the vessels; but the heart, because it is the source of the blood vessels and possesses in itself the power that first produces the blood, is reasonably composed from the same kind of nourishment it receives. We have now said why the viscera are bloodlike in form, and why some are uniform and others non-uniform. [section 1] Among the uniform parts in animals, some are soft and moist, others hard and solid. The moist ones are moist either altogether, or for as long as they remain in their natural condition — for example blood, serum, fat, suet, marrow, semen, bile, milk in those that have it, flesh, and whatever is analogous to these; for not all animals possess all of these parts, but some possess what is analogous to them in place of them. The dry and solid uniform parts are, for example, bone, fish-spine, sinew, blood vessel. For even among the uniform parts the manner of division shows a difference; for in some cases the part has the same name as the whole, as a piece of a blood vessel is called a blood vessel, while in others it does not, since no piece of a face is called a face.
8| [section 2] First, then, there are many modes of causal explanation for both the moist and the dry parts. Some of them serve as the matter of the non-uniform parts (for each of the instrumental parts is composed of these — of bones, sinews, flesh, and other such things, some contributing to its substance, others to its function); others of the moist parts serve as nourishment for these parts (for everything derives its growth from moisture); and others turn out to be residues of these, for example the sediment of dry nourishment, and, in those that have a bladder, that of moist nourishment. [section 3] The differences among these parts themselves, relative to one another, exist for the sake of the better — as, among other things, blood differs from blood: one is thinner, the other thicker; one is purer, the other more turbid; and again one is colder, the other hotter, both among the parts of a single animal (for the blood in the upper parts differs from that in the lower parts by just these differences) and from one animal to another. And in general, some animals are blooded, while others have, in place of blood, some other part of this kind.
9| [section 4] Thicker and hotter blood is more productive of strength, while thinner and colder blood is more productive of perceptiveness and intelligence. The same difference holds also for whatever exists analogously to blood; and this is why bees and other such animals are more intelligent by nature than many blooded animals, and among blooded animals, those with cold and thin blood are more intelligent than the opposite kind. Best of all are those with blood that is hot, thin, and pure at once, for such blood is well disposed both toward courage and toward practical wisdom. This is also why the upper parts show this difference as against the lower, and again the male as against the female, and the right side of the body as against the left. [section 5] In like manner one must suppose that the other parts of this kind, and the non-uniform parts too, show this same sort of difference — some bearing on the functions and substance proper to each animal, others on what is better or worse. For instance, among animals that have eyes, some have hard eyes and others moist eyes, and some have no eyelids while others do, for the sake of more accurate vision.
10| [section 6] That it is necessary to have either blood or something of the same nature as blood, and what the nature of blood is — these are things one must study by first distinguishing the causes concerning hot and cold, and then examining the causes concerning blood in the same way. For the nature of many things is traced back to these principles, and many people dispute over which animals, and which parts of animals, are hot and which are cold. Some say that aquatic animals are hotter than land animals, claiming that the heat of their nature counterbalances the coldness of their environment; and that bloodless animals are hotter than blooded ones, and females hotter than males — as Parmenides says that women are hotter than men, and certain others say the same, on the ground that the menstrual flow occurs in women because of their heat, and makes them full of blood; while Empedocles says the opposite. Further, as regards blood and bile, some say that each of the two, whichever one, is hot, others that it is cold. [section 7]
11| But if hot and cold admit of so much dispute, what must we suppose about the other qualities? For these are, for us, the most evident of all in the realm of perception. This seems to happen because 'hotter' is said in many ways; for each disputant seems to be saying something true even while contradicting the others. One must therefore not lose sight of how one ought to speak of some naturally constituted things as hot and others as cold, and some as dry and others as moist, since it seems clear that these are, roughly speaking, the causes both of death and of life, and further of sleep and waking, of maturity and old age, of disease and health — but not roughness and smoothness, nor heaviness and lightness, nor, one might say, any other such quality. And this has come about reasonably; for, as has been said elsewhere before, these are the principles of the natural elements: hot and cold, dry and moist. [section 8]
12| Is 'hot' then said in an unqualified sense, or 8 in several ways? We must grasp what the function of the hotter thing is, or how many functions, if there are several. In one way, then, a thing is called hotter when what it touches is heated more by it; in another way, what produces more perception in touching, and this if it comes with pain. But sometimes this seems to be false; for sometimes it is the state of the person perceiving that is the cause of the pain. Again, what is more capable of melting is called hotter than what is meltable, and what is more capable of burning than what is burnable. Again, if one and the same thing is present in a greater and a lesser amount, the greater amount is hotter than the lesser. Besides these there are two more: what does not cool quickly but slowly is hotter, and what is heated more quickly than what is heated slowly we say is hotter in nature, since the one is far from its contrary while the other is near to what is like it. [section 9] It is said, then, 9
13| if not in several senses, at least in this many senses, that one thing is hotter than another; and it is impossible for all these ways to belong to the same thing. For boiling water heats more than flame does, but flame burns and melts what is burnable and meltable, while water does neither. Again, boiling water is hotter than a small fire, but hot water cools both more quickly and more completely than a small fire does; for fire never becomes cold, but all water does become cold. Again, boiling water is hotter to the touch, but it cools and solidifies more quickly than oil does. Again, blood is hotter to the touch than water and oil, but it solidifies more quickly. Again, stones and iron and things of that sort heat up more slowly than water, but once heated they burn more. [section 10] 10 Besides this, of the things called hot, some have a heat that is alien to them and others have a heat that is their own, and it makes a great difference whether a thing is hot in this way or in that way; for the one comes close to being hot accidentally rather than in its own right — just as if someone were to say, if it were an accident that a feverish person happened to be musical, that the musical person is hotter than the person who is hot with health.
14| [section 11] 11 Since, then, one thing is hot in its own right and another accidentally, what is hot in its own right cools more slowly, while what is hot accidentally often heats the perception more; and again, what is hot in its own right burns more — as flame does more than boiling water — while what is hot accidentally, namely boiling water, heats more to the touch. So it is clear that judging which of two things is hotter is not a simple matter; for in one respect this thing will be hotter, and in another respect the other. [section 12] 12 Some things of this kind cannot even be said, without qualification, to be hot or not hot. For that which the underlying subject happens to be is not hot, but becomes hot in combination — as if one were to give the name 'hot' to water or to iron. For it is in this way that blood is hot. And in such cases it becomes clear that the cold is a nature and not a privation, namely in all cases where the underlying subject is hot by way of an affection. [section 13]
15| And perhaps the nature of fire itself, if this 13 is so, is of this sort too; for perhaps the underlying subject is either smoke or ember, of which the one is always hot (for smoke is an exhalation), while the ember, once extinguished, is cold. Oil and pine-wood too could become cold. And nearly all things that have been fired possess heat — for example lime and ash, and the sediments of animals, and among residues, bile — because something has been kindled in them and left behind within them as heat. In another way pine-wood and fatty things are hot, because they change quickly into the actuality of fire. Heat seems both to solidify and to melt. [section 14] Now whatever consists only of water, 14 this the cold solidifies, but whatever consists of earth, fire solidifies; and among hot things, those that are more of earth solidify quickly under cold, and irreversibly, while those that are more of water solidify reversibly. But these matters have been determined more clearly elsewhere — what things are the solidifiable ones, and for what causes they solidify. As for what is hot, and what sort of thing is hotter, since this is said in several ways, it will not belong to all things in the same way, but we must further distinguish that this thing is hot in its own right, while the other is often hot accidentally, and further that this thing is hot in potentiality while that thing is hot in actuality, and that this is hot in this way, by heating the touch more, while that is hot in that way, by producing flame and setting things ablaze.
16| [section 15] Since the hot is said in 15 many ways, it will clearly follow that the cold is spoken of according to the same account. Let this, then, be our determination concerning the hot and the cold and their superiority over one another. [section 1] 3 Next in order, following what has been said, we must go through the dry and the moist as well. These too are said in several ways, some things being so in potentiality, others in actuality. For ice, and everything moist that has solidified, is called dry in actuality and accidentally, while being moist in potentiality and in its own right; whereas earth and ash and things of this sort, once mixed with moisture, are moist in actuality and accidentally, but dry in their own right and in potentiality. When these are separated out, some of them are capable of taking up water and are moist both in actuality and in potentiality, while others are entirely of earth and dry, and it is in this way, above all, that the properly and unqualifiedly dry is spoken of. Likewise the moist too has, by the same account, what is properly and unqualifiedly so, and the same holds concerning the hot and the cold. [section 2]
17| 2 Now that these points have been determined, it is clear that blood is hot in one way — namely in the way that constitutes what it is to be blood, just as if we were to signify by a single name what boiling water is called — while the underlying subject, the thing which blood happens to be, is not hot; and in its own right it is in one way hot and in another way not. For heat will belong to it in its account, just as white belongs in the account of a white man; but insofar as blood is hot by way of an affection, it is not hot in its own right. And the same holds concerning the dry and the moist. This is why, in the nature of such things, some are hot and moist but, when separated out, solidify and appear cold, as blood does, while others are hot and have thickness, as bile does, but when separated out from the nature of the things that contain them, undergo the opposite: they become cold and moist; for blood becomes drier, while yellow bile becomes moister. We must posit that the more and the less participation in the opposites belongs to these things as inherent attributes. [section 3]
18| How, then, blood is hot, and how it is 3 moist, and how the nature of blood partakes of the contraries, has now been stated more or less fully. Since everything that grows must necessarily take in nourishment, and nourishment for all things comes from the moist and the dry, and the concoction and transformation of these comes about through the power of heat, all animals and plants alike, even if for no other reason than this, must necessarily possess a natural principle of heat; and this, like the processes of working up the nourishment, belongs to several parts. For the first function evident in animals is that carried out through the mouth and the parts in it, in all cases where the food requires division. But this is not the cause of any concoction, but rather of easy concoction; for the division of the food into small pieces makes the work easier for the heat. But the concoction proper is already carried out, with the aid of natural heat, by the upper and the lower cavity. [section 4] Just as the mouth is a passage for 4 the unworked food, and the part continuous with it, which they call the esophagus — in all animals that have this part — leads as far as the stomach, so too there must be several other starting-points through which the whole body will take up its nourishment, as though from a manger, from the stomach and from the nature of the intestines.
19| [section 5] For plants take their nourishment already worked up out of the earth by means of their roots (which is why no residue arises in plants: they use the earth and the heat in it as a stomach), while animals — nearly all of them, and the ones that move about plainly so — have, one might say, earth within themselves in the cavity of the stomach, out of which, just as plants take their nourishment by their roots, these must take theirs by some organ, until the process of the digestion that follows it reaches completion. For the work done by the mouth hands the food over to the stomach, and from the stomach it is necessary for something else in turn to receive it, which is in fact what happens: the veins stretch the whole way through the mesentery, beginning below and reaching up to the stomach. These matters must be studied from the dissections and from the Researches on Animals. [section 6] Now since there is something that receives all nourishment and the residues that arise from it, and the veins are like a vessel for blood, it is clear that blood is the final nourishment for the animals that have blood, and for the bloodless ones the analogous substance. And because of this, when animals do not take in nourishment this substance runs low, and when they do it increases, and when it is good, this is healthy, and when it is bad, this too is bad. That blood, then, exists for the sake of nourishment in the blooded animals is clear from this and from considerations like it. And indeed this is also why blood, when touched, produces no perception, just as none of the other residues does either.
20| [section 7] Nor is the nourishment itself like flesh; for flesh, when touched, does produce perception. For blood is not continuous with flesh, nor grown together with it, but lies as though in a vessel, both in the heart and in the veins. As for the manner in which the parts take their growth from it, and about nourishment in general, it is more fitting to go through this in the works on generation and elsewhere. For now let this much be said — for this much is useful — that blood exists for the sake of nourishment, and for the nourishment of the parts. [section 1] The things called fibers: some blood has them, some does not, for example that of deer and roe deer. That is why blood of this kind does not congeal; for of blood, the part that is more watery is colder, and this is why it does not congeal, while the earthy part congeals as the moisture evaporates along with it; and the fibers are of earth. [section 2] It happens that some animals of this kind also have a keener intelligence, not because of the coldness of the blood, but rather because of the
21| fineness of it, and because it is pure; for the earthy element has neither of these qualities. For those animals whose fluid is finer and purer have a more readily-moved perception. And this is also why some of the bloodless animals have a more intelligent soul than some of the blooded ones, as has been said before — for example the bee and the race of ants, and anything else of that kind. But the excessively watery ones are more cowardly. For fear chills; the animals that have this kind of blend in the heart are therefore already predisposed toward that affection, since water is congealed by cold. This is why the other bloodless animals are, generally speaking, more cowardly than the blooded ones, and become motionless in fear, discharge residues, and some of them even change their color. [section 3] But animals that have very many fibers, and thick ones, are more earthy in nature and spirited in character, and prone to lose themselves in that spirit. For spirit produces heat, and solid things, once heated, heat more than fluids do; and fibers are solid and earthy, so that they become like fomentations in the blood and cause a seething in fits of spirit. This is why bulls and boars are spirited and prone to lose themselves; for their blood is the most fibrous, and that of the bull in particular congeals fastest of all.
22| [section 4] But once these fibers are removed, the blood does not congeal; for just as if one were to remove the earthy element from mud, the water would not congeal, so too with blood: the fibers are of earth. But if they are not removed, it congeals, like moist earth under cold; for as the heat is squeezed out by the cold, the moisture evaporates along with it, as has been said before, and it congeals not by heat but by being dried out under cold. In living bodies it remains fluid because of the heat present in animals. [section 5] The nature of the blood is responsible for much, both as regards the character of animals and as regards their perception, and reasonably so; for it is the matter of the whole body, since nourishment is matter, and blood is the final stage of nourishment. It therefore makes a great difference whether it is hot or cold, fine or thick, murky or pure. Serum is the watery part of the blood, present because the blood has not yet been concocted, or because it has spoiled; so that the one kind of serous fluid arises of necessity, while the other exists for the sake of the blood. [section 1]
23| Fat and suet differ from each other according to a difference in the blood. For each of them is blood that has been concocted through good nourishment, the part not used up for the fleshy portion of the animals, which is well-digested and well-nourished. Their oiliness shows this; for among fluids, the oily is what is common to air and fire. This is why none of the bloodless animals has either fat or suet, because they have no blood either. Among the blooded animals, those whose blood is more corporeal have suet rather than fat. For suet is earthy, and this is why it congeals, just as the fibrous kind of blood does too, both itself and broths of that kind; for it has little water, but much earth. [section 2] This is why animals that do not have teeth in both jaws but instead have horns have suet. Their nature is evidently full of this kind of element, in that they are horn-bearing and have ankle-bones; for all such things are dry and earthy in nature. But animals with teeth in both jaws, and without horns, and many-toed, have fat instead of suet, which does not congeal, nor does it crumble when dried, because its nature is not earthy. [section 3] Now these substances, when present in moderate amount in the parts of animals, are beneficial (for they do not hinder perception, and they contribute an aid toward health and strength), but when they exceed due measure in quantity they destroy and harm. For if the whole body were to become fat and suet, it would perish;
24| for an animal is what it is in virtue of its perceptive part, and flesh, and the analogous part, is what perceives; but blood, as has been said before too, has no perception, and so neither do fat and suet, for they are concocted blood. So that if the whole body were to become of this kind, it would have no perception at all. This is also why animals that are excessively fat grow old quickly; for they have little blood, since the blood is used up in the production of fatness, and animals with little blood are already predisposed toward decay; for decay is a kind of deficiency of blood, and what is little in quantity is susceptible to being acted on by cold of any degree, and by heat as well. And indeed fat animals are also less fertile, for the same reason: [section 4] for what ought to go from the blood into the seed and the semen is instead used up for fat and suet; for it is by the blood being concocted that these come to be, so that either no residue at all arises for such animals, or only a little. And concerning blood and serum and fat and suet, what each of them is and through what causes, has been stated. [section 1]
25| Marrow, too, is a kind of state of blood, and not, as some think, a seminal power belonging to semen. This is entirely clear in the young: since the parts are formed out of blood, and the nourishment for embryos is blood, even in the bones the marrow is blood-like. But as animals grow and the blood is concocted, just as the other parts change and the viscera change color (for while animals are still young, each of the viscera is excessively blood-like), so too does the marrow change: in animals that are fatty, it is oily and resembles fat, while in those in which the blood, when concocted, does not become like fat but becomes suet, in these the marrow is suet-like. Hence in horned animals that lack teeth in the upper jaw the marrow is suet-like, while in animals that have teeth in both jaws and are many-toed it is fatty. [section 2] 2 The spinal marrow is least of this kind, because it must be continuous and extend through the whole spine, which is divided at the vertebrae; being oily or suet-like, it would not be equally continuous, but would be either brittle or fluid. Some animals have no marrow worth mentioning — those whose bones are strong and dense, as with the lion; for the lion's bones, because they have no cavity at all, seem to have no marrow whatsoever.
26| [section 3] 3 Since it is necessary that animals possess the nature of bones, or what is analogous to bones — for example, water-animals have the spine in place of bones — it is necessary that some of them also have marrow, since the nourishment out of which the bones are formed is enclosed within them. That the nourishment for all animals is blood has been said earlier. And it stands to reason that the marrows are suet-like and fatty: for on account of the warmth produced by being enclosed within the bones, the blood is concocted, and the concoction of blood taken by itself is suet and fat. [section 4] 4 And so, among animals having dense and strong bones, it is reasonable that in some there is no marrow, and in others little; for the nourishment is used up into the bones. In those animals that do not have bones but a spine instead, the spinal marrow alone is marrow; for such animals are by nature low in blood, and the only hollow part is that of the spine. Hence marrow comes to be in this part alone: it alone has room for it, and it alone needs a binding because of its many divisions at the joints. This is why the marrow here, as has been said, is somewhat different in kind: because it takes the place of a ligament, it is sticky and sinewy, so that it may have tension.
27| [section 5] 5 Why, then, those animals that have marrow have it has been stated; and from this it is also clear what marrow is: it is a portion of the blood-nourishment going to the bones and the spine, namely the residue enclosed within them once it has been concocted. [section 1] 7 Concerning the brain, the discussion is very nearly continuous with this one; for to many people the brain too seems to be marrow, and the source of the marrow, because they observe the spinal marrow continuous with it. But its nature is, so to speak, entirely opposite: the brain is the coldest of the parts in the body, while marrow is hot by nature — its oiliness and fattiness make this clear. This is why the spinal marrow is continuous with the brain: nature always contrives, as a help against the excess of each thing, the neighboring presence of its opposite, so that the one may balance out the excess of the other. [section 2] 2 That marrow is hot, then, is clear from many things. The coldness of the brain is evident both by touch, and further from the fact that it is the least blood-like of all the fluids in the body — it contains not the slightest amount of blood in it — and the driest. It is neither a residue nor one of the continuous parts, but has a nature of its own, and reasonably so.
28| [section 3] 3 That it has no continuity at all with the perceptive parts is clear both from observation, and still more from the fact that it produces no perception when touched, just as neither blood nor the residue of animals does. It exists in animals for the preservation of the whole of their nature. For some place the soul of the animal in fire or some such power, putting the matter crudely; but it is perhaps better to say that the soul is constituted within some such body. The reason for this is that heat is the most serviceable of bodies for the works of the soul; for nourishing and causing motion is the work of the soul, and these come about above all through this power. It is therefore much the same to say that the soul is fire as to say that the carpenter is the drill, or the saw, or his craft (the text here is defective) — for the work is completed by these instruments only when they act in close conjunction with one another. That animals must, then, share in heat is clear from these considerations, [section 4]
29| 4 clear from these considerations; and since everything needs the countervailing inclination, so as to hit upon the moderate and the mean (for the mean has the substance and the ratio proper to the thing, whereas neither extreme has it by itself), for this reason nature has contrived the brain in relation to the region of the heart and the heat within it, and it is for the sake of this that this part exists in animals — having a nature common to water and earth. And because of this all the blooded animals have a brain, while none, so to speak, of the others do, except that in some there is an analogous part, as with the octopus; for all bloodless animals have little heat because of their lack of blood. [section 5] 5 The brain, then, makes well-tempered the heat and boiling in the heart; and so that this part too may attain a moderate heat, from each of the two vessels — both the great vein and the so-called aorta — veins run and terminate in the membrane around the brain. And so that it should not be harmed by the heat, instead of a few large veins, many fine, thin veins surround it, and instead of much thick blood, thin and pure blood surrounds it. This is also why discharges in the body take their origin from the head, in those animals whose parts around the brain are colder than the well-tempered mixture requires: for as the nourishment rises in vapor upward through the veins, the residue, being cooled owing to the capacity of this region, produces discharges of phlegm and serum.
30| [section 6] 6 One must grasp — comparing something small to something great — that this happens in a way similar to the generation of rain: for as vapor rises from the earth and is carried by the heat toward the region above, when it comes to be in the air above the earth, which is cold, it condenses again into water because of the cooling, and flows back down toward the earth. [section 7] 7 But it is fitting to speak of these matters in the treatises on the origins of diseases, so far as it belongs to natural philosophy to speak of them. This part also produces sleep in the animals that have a brain, and the analogous part does so in those that do not. For by cooling the influx of blood coming from the nourishment — or also through certain other, similar causes — it weighs down the region (which is why those overcome by sleep feel heaviness in the head), and it makes the heat retreat downward together with the blood. Hence, being gathered in greater quantity in the lower region, it brings about sleep, and it takes away the capacity to stand upright — in those animals that are upright by nature, the capacity to stand upright as a whole, and in the others, the uprightness of the head. Concerning these matters it has been discussed on its own account in the treatises on perception and on sleep.
31| [section 8] That the brain is a compound of water and earth is shown by what happens to it: when boiled, it becomes dry and hard, and the earthy part is left behind once the water has evaporated under the heat — just as with the boiled preparations of pulses and other fruits, because most of their bulk is earth, and the moisture mixed in departs; for these too become hard and thoroughly earthy. [section 9] Among animals, man has the largest brain in proportion to his size, and among human beings, the males have larger brains than the females; for the region around the heart and lung is hottest and richest in blood. This is also why man alone among animals stands upright: for the nature of the hot, gaining strength, produces growth away from the middle, in the direction of its own motion. Now opposed to a great deal of heat is a greater amount of moisture and cold, and because of this abundance the bone around the head — which some call the bregma — hardens latest of all, since for a long time the heat is evaporating off much moisture; this happens to none of the other blooded animals. [section 10]
32| Man also has the most sutures around the head, and the male more than the female, for the same reason: so that the region may be well-ventilated — and the more so the larger the brain is. For a brain that becomes too moist or too dry will not perform its own function, but will fail either to cool the heat or to make it congeal, so that it produces diseases, derangements, and deaths; for the heat in the heart, which is the principle, is most sympathetically affected and quickly registers perception whenever the blood around the brain undergoes some change and is affected. [section 11] Concerning the fluids that are innate in animals, virtually everything has now been said; but of those that arise later, there are the residues of nutriment — the sediment of the bladder and that of the belly — and besides these, seed and milk, in those animals whose nature it is to have each of these. Now the residues of nutriment have their own proper account in the inquiry and study concerning nutriment — in which animals they occur and for what causes; but the matters concerning seed and milk belong among the writings on generation, for the one is a principle of generation, the other is for the sake of generation.
33| [section 1] We must now examine the other uniform parts, and first flesh, in those animals that have flesh, and in the others whatever is analogous to it; for this is a principle and, in its own right, the body of animals. This is clear also from the account: we define an animal by its having perception, and first of all the first and most basic perception; and this is touch, and the organ of perception for this is a part of the kind just described — either the primary organ itself, as the pupil is of sight, or that which comprehends it together with its surroundings, as if one were to add to the pupil the whole of the transparent medium. Now in the case of the other senses it was both impossible and of no advantage for nature to make this so, but for the sense of touch it is necessary; for this alone, or most of all, among the sense-organs is bodily. [section 2] But it is evident from perception that all the other parts exist for the sake of this — I mean, for example, bones and skin and sinews and veins, and further hair and the class of nails, and anything else of this kind. For the nature of bones, hard by nature, has been contrived for the safety of what is soft, in those animals that have bones; while in those that do not, the analogous part serves this purpose, as in fish, in some the spine, in others cartilage.
34| [section 3] Now some animals have this kind of protection on the inside, but some of the bloodless animals have it on the outside, as each of the soft-shelled creatures does — crabs, for instance, and the class of crayfish — and likewise the class of shelled creatures, such as the so-called oysters; for in all of these the fleshy part is inside, while the earthy part, which holds together and protects, is outside. For besides guarding their continuity, since their nature contains little heat, being bloodless, the shell surrounds and preserves the smoldering heat within, like some covering set around it. [section 4] The tortoise and the class of terrapins seem to be constituted similarly to these, though a different class from them. But insects and cephalopods are put together in a way opposite both to these and to each other, in contrary fashion; for neither seems to have anything bony, nor any earthy part set apart worth mentioning, but the cephalopods are almost entirely fleshy and soft, though, so that their body may not be easily destroyed, unlike the merely fleshy animals, their nature is intermediate between flesh and sinew: it is soft like flesh, but has tension like sinew; and its flesh splits not in a straight line but is divisible in circles, for constituted this way it would be most useful for strength.
35| [section 5] In them there is also present what is analogous to the spines of fish: in cuttlefish, what is called the cuttlebone, and in squid, what is called the sword. Octopuses have nothing of this kind, because the receptacle called the head is small in them, whereas in the others it is elongated; and that is why nature has sketched in these structures, for the sake of their straightness and rigidity, just as among blooded animals it gives bone to some and spine to others. [section 6] Insects, however, are constituted in a way opposite both to these and to blooded animals, as we said. For they have nothing distinctly hard and nothing distinctly soft, but the whole body is hard, with a hardness of this sort: fleshier than bone, but bonier and earthier than flesh, so that their body may not be easily divided. [section 1] The nature of the bones and the nature of the veins are alike. For each of them, beginning from one point, is continuous, and no bone is anything in its own right by itself, but is either a part of a continuous whole, or is joined and bound to another, so that nature may use it both as one and continuous, and as two and divided, for the sake of bending.
36| [section 2] Likewise, too, no vein exists by itself in its own right, but all are part of one. For if any bone were separate, it would not perform the function for the sake of which the nature of bones exists — for, not being continuous but broken off, it would be the cause neither of bending nor of any rigidity — and further it would do harm, lodged in the flesh like some kind of dart. And if some vein were separate and not continuous with the source, it would not preserve the blood within it; for it is the heat coming from that source which prevents the blood from congealing, and what is separated is also observed to putrefy. [section 3] The heart is the source of the veins, and what is called the spine is the source of the bones, in those animals that have bones, and it is from this that the nature of the other bones continues; for it is the spine that holds together the length and the straightness of animals. Since, when the animal moves, its body must necessarily bend, the spine is one thing on account of its continuity, but many-parted through the division into vertebrae. From this, in those animals that have limbs continuous with it, the bones of these limbs are joints, at the points where the limbs bend, bound together with sinews; and their extremities fit together, one being hollow and the other rounded, or both hollow and enclosing something between them, like a peg, an astragalus, so that bending and extension may occur; for otherwise such motion would be either altogether impossible, or would not be performed well.
37| [section 4] Some of them, the starting point of one being similar to the end point of the other, are bound together by sinews. And there are cartilaginous parts between the joints, like padding, so that they do not rub against one another. The flesh has grown around the bones, wrapped beforehand in thin, fibrous bonds, for the sake of which the class of bones exists. [section 5] For just as those who mold an animal out of clay, or some other moist material, first set up underneath some solid body, and then mold the material around it in this way, in the same manner nature has fashioned the animal by building the flesh around the bones. In the other fleshy parts, then, bones underlie them: in the parts that move by bending, for the sake of this bending; in the immobile parts, for the sake of protection — as the ribs that close around the chest do, for the safety of the organs around the heart. But the region around the belly is boneless in all animals, so that it will not hinder the swelling that necessarily occurs in animals from their food, and in females, the growth of the embryos within them. [section 6] Now the animals that bear live young have, both internally and externally, a similar and strong power of bone. For all such animals are, proportionally speaking, much larger in body than the non-viviparous ones; for in some places many of the viviparous animals grow large, as in Libya and in hot, dry regions.
38| [section 7] Large animals need stronger supports, both bigger and harder, and among these, the more violent animals need still harder ones. This is why the bones of males are harder than those of females, and so are those of flesh-eating animals, since their food comes through fighting — as with the lion's: these are so hard by nature that they strike sparks like fire out of stones when struck. The dolphin, too, has not fish-spines but bones, since it bears live young. [section 8] In animals that are blooded but do not bear live young, nature varies by small degrees; birds, for instance, have bones, but weaker ones. [section 9] Among fish, the egg-laying ones have fish-spine, and in snakes too the nature of the bones is spiny, except in the very large ones; these, for the same reasons as the viviparous animals, need stronger supports for the sake of strength. But the so-called cartilaginous fish have a nature of cartilage-spine; for their motion must necessarily be more supple, so that their supports, too, must not be brittle but softer, and nature has spent all the earthy material on the skin. At the same time nature is unable to distribute the same surplus into many places at once.
39| [section 10] Also among the viviparous animals, many of the bones are cartilaginous, wherever it is advantageous for the solid material to be soft and spongy because of the flesh lying around it, as happens with the ears and the nostrils; for brittle material breaks quickly in projecting parts. Cartilage and bone are the same in nature, but differ by more and less; hence, too, neither one grows back once cut off. Now among land animals, cartilage has no marrow of its own, separate within it; for marrow, when it is separated out and mixed all through, makes the composition of the cartilage soft and spongy. [section 11] In the cartilaginous fish, the spine is cartilaginous but does have marrow; for this part serves them in place of bone. Close to bone in nature, too, are such parts as claws, hooves, talons, horns, and the beaks of birds. All these exist in animals for the sake of assistance; for the wholes composed out of them, which share the same name as the parts — a whole hoof, a whole horn — have been devised for the safety of each animal. In this same class, too, belongs the nature of teeth, which in some animals serves one function, the working of food, while in others it serves both this and defense, as in all the animals with jagged teeth and tusks.
40| [section 12] All these parts necessarily have an earthy and solid nature, for this is the capacity a weapon needs. This is why all such parts belong more to the four-footed viviparous animals than to the human race, because their whole composition is more earthy than that of the human race. [section 13] But about these parts, and those connected with them — such as skin, bladder, membrane, hair, feathers, their analogues, and any other part of this kind — we must examine their cause later, together with the non-uniform parts, and for the sake of what each is present in animals; for it will be necessary to recognize these too, as with those others, from their functions. [section 14] But because these parts share the same name as their wholes, they have now taken their place in the account of the uniform parts. The principles of all of them are bone and flesh. As for semen and milk, we left these aside in the discussion of the fluid uniform parts; for the inquiry into them fits better with the accounts of generation, since one of them is a principle and the other is nourishment for the things that come to be. [section 1]
41| 10 Let us now speak again as if from the beginning, starting first from first things. For in all complete animals there are two most necessary parts: that by which they take in food, and that by which they will discharge the residue; for it is not possible either to exist or to grow without food. Now plants — for we say that these too live — have no place for useless residue; for they take their food from the earth already concocted, and in place of a residue they put forth seeds and fruits. A third part is present in all of them, the middle between these two, in which — [section 2] Now the nature of plants, being stationary, is not multiform in its non-uniform parts; for the use of few organs serves few actions. Hence their shape must be studied on its own terms. But the things that, besides living, also have perception have a more multiform shape, and some of these more so than others — and a richer one still, in those whose nature partakes not only of living but also of living well. [section 3] Such is the human race; for among the animals known to us, it either alone shares in the divine, or does so most of all. So both for this reason, and because the shape of its external parts is most familiar to us,
42| we must speak about this animal first. For it is in this animal alone that the parts naturally situated upward are upward in relation to the whole; for man alone among animals stands upright. [section 4] Now the fact that the head is fleshless follows necessarily from what has been said about the brain. For it is not, as some say, that if it were fleshy the race would be longer-lived; rather, they say it is fleshless for the sake of good perception — for, they say, one perceives with the brain, and parts that are too fleshy do not admit of perception. [section 5] Neither of these claims is true. If the region around the brain were fleshy, it would produce the very opposite of what the brain exists in animals for — since it would not be able to cool the body if it were itself too warm — and the brain is not the cause of any of the perceptions, since it is itself as devoid of perception as any other residue. But since they cannot find the real cause why some of the perceptions are located in the head in animals, and they see that the head is more distinctive than the other parts, they pair the two together by inference, from one to the other. [section 6]
43| That the region around the heart is the starting point of the senses has been settled earlier, in the treatise on sense-perception. So too has the reason why two of the senses are plainly dependent on the heart -- that of touch and that of flavors -- while, of the remaining three, smell holds a middle position, and hearing and sight are located mainly in the head, because of the nature of their organs; and of these, sight is so located in every animal that has it, since hearing and smell, in the case of fish and similar animals, make what has been said evident: they hear and they smell, yet they have no organ for these sensibles that is visible in the head. Sight, in every animal that has it, is reasonably situated around the brain: the brain is moist and cold, and the substance of the eye is water in nature; for water is the most easily preserved of transparent things. [section 7]
44| Further, the more precise of the senses must occur through the parts that have the purer blood, since the motion of the heat in the blood blunts the activity of perception. For these reasons the organs of these senses are in the head. And it is not only the front of the head that is fleshless, but the back of it as well, because in every animal that has a head this part must be held very upright; for nothing can hold itself upright while carrying a load, and a load is exactly what it would carry if the head were covered in flesh. This also makes clear that the head is fleshless not for the sake of the brain's perception; for the back of the head has no brain, yet is fleshless all the same. [section 8] And some animals reasonably have their hearing too situated in the region around the head: for what is called the empty space is full of air, and we say that the organ of hearing consists of air. Now from the eyes the passages lead into the veins around the brain; and likewise, again, from the ears a passage connects through to the back of the head. [section 9] All the animals that have this part have the brain toward the front, because that which perceives is in front, and perception proceeds from the heart, and the heart lies among the forward parts, and perceiving occurs through the blood-bearing parts, while the cavity at the back is empty of veins. The organs of sense have, in this way, been arranged well by nature,
45| the organ of hearing at the middle of the circumference (for one hears not only along a straight line but from every direction), while sight is set toward the front (for one sees along a straight line, and motion is toward the front, and one must see ahead in the direction of that motion). And the organ of smell is reasonably placed between the eyes. For each of the sense organs is double, because the body is double, one part right and one left. [section 10] In the case of touch this is not evident; the reason is that the primary organ of touch is not the flesh or such a part, but something internal. In the case of the tongue it is less evident than in the other senses, but more evident than in the case of touch, since taste too is a kind of touch. Yet even here it is evident, since the tongue is seen to be split. In the other sense organs the doubleness of the perception is more plainly evident: there are two ears and two eyes, and the power of the nostrils is likewise twofold. [section 11] If it were placed differently and set apart, as the organ of hearing is, it would not perform its own function, nor would the part in which it lies; for in animals that have nostrils, perception of smell occurs by way of breathing, and this part lies in the middle and among the forward parts. This is why nature has brought the nostrils together into the middle of the three sense organs, setting them, as it were, on a single line for the motion of breathing. And in the other animals too these sense organs are well placed, each according to its own particular nature.
46| [section 1] Quadrupeds have their ears set apart and, it might seem, above the eyes. But this is not so -- it only appears so because these animals are not upright but stoop. Ears that are raised up and mobile are useful to animals that move about a great deal, since by turning they catch sounds better from every direction., since, being raised up and mobile, they catch sounds better from every direction by turning about. [section 1] Birds have only the passages for hearing, because of the hardness of their skin, and because they have not hair but feathers; so they have no material of the kind out of which ears could be formed. The same holds likewise of those quadrupeds that lay eggs and are scaly, for the same account fits their case too. And the seal, among the live-bearing animals, likewise has no ears but only passages for hearing, because it is a quadruped whose form has been stunted. [section 1] Human beings, birds, and both the live-bearing and the egg-laying quadrupeds have a protective covering for the eye: the live-bearing animals have two eyelids, with which they also blink; among birds, the heavy-bodied ones and others besides, along with the egg-laying quadrupeds, close the eye with the lower lid; birds blink by means of a membrane from the corners of the eyes. The reason they have this protection is that their eyes are moist, so that, in this way, they may see sharply, as nature intends. For if their eyes had a hard skin they would be less liable to injury from things striking them from outside, but they would not see sharply.
47| [section 2] For this reason the skin around the pupil is thin, and the eyelids exist for the sake of safety; and this is why all animals blink, human beings most of all -- all of them so as to keep off what strikes against the eyelids (and this is not done by choice, but nature has made it so), and human beings most often of all because their skin is the thinnest. The eyelid is skin wrapped around the eye; this is also why neither the eyelid nor the foreskin ever grows fused together, since these are skin without flesh. [section 3] Those birds that close the eye with the lower lid, and the egg-laying quadrupeds, close it this way because of the hardness of the skin around the head. The heavy-bodied among the winged animals, since they are not fliers, have the growth that would otherwise have gone into feathers turned instead into thickness of skin. This is why these close their eyes with the lower lid, while pigeons and the like use both lids. [section 4] The quadrupeds among the egg-laying animals are scaly; and scales are in every case harder than hair, so that their skins are harder than ordinary skin as well. The skin around their head, then, is hard, and this is why they have no eyelid there, while the skin below is fleshy, so that the lower lid has thinness and can be stretched. The heavy-bodied birds do not blink by means of this lower lid but by means of the membrane, because the motion of the lid is slow, whereas blinking must happen quickly; and the membrane is of just this quick kind.
48| [section 5] They blink from the corner of the eye nearest the nostrils, because it is better that their nature proceed from a single starting point, and this is the starting point they have -- the point of attachment toward the nostril; and the forward part is more of a starting point than the side part. Quadrupeds that lay eggs do not blink in the same way, because, being creatures of the ground, they have no need of moist and precise vision. Birds do need it, however, since their use of sight is at a distance. This is why the hook-taloned birds have sharp sight -- their view of their food is from above, which is also why these fly highest of all birds -- while the ground-dwelling birds that are not fliers, such as chickens and the like, do not have sharp sight, since nothing in their way of life presses them toward it. [section 6] Fish, insects, and the hard-shelled animals have eyes that differ from these, and none of them has an eyelid. The hard-shelled animals have none at all; for the function of the eyelid is a quick action performed by skin, and instead of this protection all these animals have hard eyes, seeing, as it were, through an eyelid that has grown fused to the eye. But since it is necessary that, because of this hardness, their sight be rather dull
49| ...to see, nature made the eyes of insects movable, and even more so in the hard-shelled animals, just as some four-footed animals move their ears, so that by turning toward the light and receiving its ray they may see more sharply. [section 7] 7 Fish, on the other hand, have moist eyes. For creatures that move about a great deal need to use their sight from far off. Now for land animals the air is easy to see through; but for fish, since water is unfavorable to sharp vision, yet does not present as many obstructions to sight as air does, for this reason they do not have an eyelid (for nature does nothing in vain), while against the thickness of the water they have moist eyes. [section 1]
50| 14 All creatures that have hair have eyelashes on their eyelids, but neither birds nor scaly animals have any, since they have no hair. As for the Libyan ostrich, we shall state the reason later, for that animal does have eyelashes. And of the creatures that have hair, only human beings have it on both sides of the body. For the four-footed animals do not have hair on their underside, but rather on their upper side; humans, by contrast, have more hair on their underside than on their upper side. For hair exists for the sake of covering in those creatures that have it; now for four-footed animals the upper side needs covering more, and while the front parts are more honorable, they become smooth because of their bending; but for humans, since because of their uprightness the front stands equal to the back, nature has assigned its help to the more honorable parts. For a cause, working from what is possible, always aims at what is better. [section 2] 2 And for this reason none of the four-footed animals has an eyelash on the lower eyelid, though in some, sparse hairs grow beneath that eyelid; nor do they have hair in the armpits or on the pubic region, as humans do; instead, in place of these, some are shaggy with hair over the whole of their upper side, as the dog family is, others have a mane along the neck, as horses and similar animals do, and others have a mane about the head, as the male lion does.
51| [section 3] 3 Further, whatever animals have tails of length, nature has adorned these too with hair — in those with a small stock of a tail, with long hair, as with horses, in those with a long tail, with short hair, and this follows the nature of the rest of the body's marking as well. For everywhere nature gives back, taking from one part to add to another. In those whose body it has made excessively shaggy, the region around the tail is correspondingly deficient in hair, as happens in the case of bears. [section 4] 4 As for the head, man is the shaggiest of animals there, of necessity because of the moistness of the brain and because of the sutures (for where moisture and heat are greatest, there growth must necessarily be greatest too), and also for the sake of help, so that the hairs may shelter the head, guarding against extremes of cold and heat. And since the human brain is the largest and the moistest, it needs the most protection of all; for what is moistest both boils and is chilled the most, while what is in the opposite condition is least affected. [section 5] 5 But it has happened that we digressed onto these points while staying close to the cause concerning the eyelashes, because of their kinship with it; so the remaining points must be given their due mention in their proper places.
52| [section 1] The eyebrows and the eyelashes both exist for the sake of protection: the eyebrows against fluids running down, so that, like an overhanging eave, they may keep off the fluids coming from the head; the eyelashes for the sake of things falling against the eyes, just as some people build palisades in front of enclosures. [section 2] 2 The eyebrows lie upon a joining of bones, which is why in many people, as they grow old, they become so shaggy that they need trimming; the eyelashes lie at the end of small blood vessels, for where the skin comes to an end, there the small vessels also reach the end of their length. So it is necessary that, because of the moisture passing off there — being bodily in nature — unless some function of nature prevents it for another use, hairs should form of necessity in these places, and for this reason as well. [section 1] 16 Now in the other four-footed, live-bearing animals, the organ of smell is not, in a certain way, far separated from the rest; but those that have elongated jaws drawn out to a narrow point have the part belonging to the nostrils present within what is called the snout, in whatever way is possible, while in the others it is more distinctly articulated in relation to the jaws.
53| [section 2] 2 The elephant has this part most peculiar to itself among the other animals; for it has both extraordinary size and extraordinary power. It is a nostril by which the animal brings its food, using it as if it were a hand, to its mouth, both dry food and wet, and by coiling it around trees it pulls them up, and uses it just as if it were a hand. For the animal's nature is at once marsh-dwelling and land-dwelling, so that, since it happens to take its food from moist ground, but as a land animal and a blooded one it must breathe, and cannot make a quick change from the moist element to the dry, as some blooded, live-bearing, breathing animals do, since its size is so exceedingly great, it must make use of the watery element in the same way as it does the land. [section 3] 3 Just as some divers provide themselves with instruments for breathing, so that by remaining a long time in the sea they may draw in air from outside the water through the instrument, so nature has made the size of the nostril such a thing for elephants. This is why they breathe by raising the nostril up above the water, whenever they happen to make their way through water; for as we have said, the trunk is a nostril for elephants.
54| [section 4] 4 But since it was impossible for the nostril to be of this kind without being soft and able to bend (for otherwise its length would get in the way of taking food from outside, just as they say horns do for oxen that graze backward — for they say those animals graze while retreating backward), given then that the nostril is of this kind, nature makes further use of it, as it is accustomed to do, applying the same parts to more than one purpose, in place of the use of the front feet. For the many-toed four-footed animals have their front feet in place of hands, and not only for the sake of supporting their weight; and elephants are among the many-toed animals, and their feet are neither cloven nor single-hoofed. But since the animal's size and the weight of its body are great, its feet exist only for the sake of support, and because of their slowness and their unfitness for bending they are of no use for anything else. [section 5] 5 So then, it has a nostril for the sake of breathing, just as each of the other animals that have lungs does, but because of its living in water and the slowness of its transition from there, it has one able to coil and be long; and since the use of the feet has been taken away, nature, as we said, makes use of this part as well for the help that would otherwise have come from the feet.
55| [section 6] Birds and snakes, and the other blooded and egg-laying four-footed animals, have the passages of the nostrils in front of the mouth, so that one might call them nostrils, if not by their working, they do not have them clearly articulated; but a bird is such that one would say it has nothing one could call a nose at all. This comes about because it has, instead of jaws, what is called a beak. [section 7] The nature of birds has its food-getting apparatus put together in this way. For a bird is two-footed and winged, so that its neck and head must of necessity be light in weight, and likewise its chest is narrow. So then, in order that it may be useful both for defense and for feeding, birds have a bony beak, and it is narrow because of the smallness of the head. In the beak they have the passages of smell, and it is impossible for them to have nostrils. [section 8] Concerning the other animals that do not breathe, it has been said earlier for what cause they do not have nostrils, but some perceive smells through the gills, some through the blowhole, and the insects through the diaphragm-like membrane, and all are moved, as it were, by the connate breath within the body; and this belongs to all of them by nature and is not brought in from outside.
56| [section 9] Below the nostrils is the nature of the lips, in those blooded animals that have teeth. For in birds, as we said, the beak is bony because of feeding and defense; for it has been drawn together into one thing in place of both teeth and lips, just as if someone were to take away a man's lips and fuse the upper teeth together separately and the lower ones separately, and draw each forward, making them long and narrow on both sides: this would already be a bird-like beak. [section 10] In the other animals, then, the nature of the lips exists for the preservation of the teeth and for their protection; and so, just as those animals share in precision and fineness of form or the opposite, so too they have this part more or less articulated. But humans have soft lips, fleshy, and capable of being separated, both for the protection of the teeth, as in the other animals, and even more so for the sake of the good; for these too serve the use of speech. For just as nature made the tongue not like that of the other animals, using it doubly for two functions, as we said she does in many cases, 660a the tongue for the sake both of tastes and of speech, so too the lips serve both this purpose and the guarding of the teeth.
57| [section 11] For speech, uttered through the voice, is composed of the letters, and if the tongue were not of such a kind, nor the lips moist, it would not be possible to sound most of the letters; for some are formed by contacts of the tongue, others by closures of the lips. What kinds of these there are, and how many, and what differentiae they have, one must inquire from those who study meter. [section 12] It was necessary that each of these two parts should immediately be well-fitted for the use described, and have such a nature as this; hence they are fleshy. The flesh of human beings turned out to be the softest. This is because man is the most perceptive of animals with respect to the perception through touch. [section 1] Below the palate, in the mouth, is the tongue, present in animals — in land animals nearly alike in all, but in the others unlike, both among themselves and in comparison with the land animals. [section 2] Man, then, has a tongue that is especially free and soft, and broad, so that it may be useful for both functions: for the perception of tastes (for man is the most perceptive of the other animals, and a soft tongue is most sensitive to touch, and taste is a kind of touch), and for the articulation of the letters and for speech; and it is the soft and broad tongue that is
58| useful; for being of such a kind and free, it can best contract and thrust forward in every direction. This is shown in those whose tongue is not overly free: they lisp and stammer, and this is a deficiency in the letters. [section 3] In being broad it is also narrow in a sense; for in the large is contained the small, but in the small there is not the large. This is why, among birds, those that utter the most articulate sounds have broader tongues than the rest. The blooded, live-bearing four-footed animals have a brief articulation of voice; for they have a tongue that is hard and not free, and thick. [section 4] Of birds, some have many notes, and the hook-taloned ones have a broader tongue. The smaller birds have more notes. And all of them use the tongue also for communication with one another, though some more than others, so that in some cases there seems even to be learning from one another; this has been discussed in the researches concerning animals. [section 5] Of land animals that are egg-laying and blooded, most have a tongue useless for the production of voice, both fastened down and hard; but for the tasting of flavors, snakes and lizards have a long, forked tongue — snakes so long that it extends from a small base to a great length, and forked, with the tip thin and hair-like, because of the gluttonous character of their nature; for they gain a double pleasure from flavors, having as it were a double organ of the perception of taste.
59| [section 6] The bloodless animals, too, have the part that perceives flavors, and so do all the blooded ones; for even those that most people think do not have it, such as some fishes, these too have in a way a sticky such part, and much the same as in river crocodiles. [section 7] Most fish do not appear to have it, for some reasonable cause: for the region of the mouth in all such animals is spiny, and because the perception of flavors in water-dwellers occupies only a short time, just as its use is brief, so too its articulation is brief. And the passage into the stomach is quick, because it is not possible for them to linger extracting the flavor; for the water would rush in meanwhile. Hence, unless one tilts open the mouth, this part does not appear to be separate at all. [section 8]
60| This region is spiny; for it is composed out of the meeting-place of the gills, whose nature is spiny. In crocodiles, something also contributes to the deficiency of this part: the fact that they have the lower jaw immoveable. For the tongue is naturally attached to the lower jaw, but crocodiles have it as it were the other way round, with the upper jaw moving; for in the others the upper jaw is immoveable. They do not have the tongue attached to the upper jaw, then, because that would work against the entrance of food, but to the lower jaw, because the upper is as it were displaced. Further, it has also come about for the crocodile, though it is a land animal, to live the life of a fish, so that for this reason too it necessarily has this part unarticulated. [section 9] Many fish, too, have a fleshy palate, and some river fish have one exceedingly fleshy and soft, such as the so-called carp, so that to those who do not examine closely it seems to have a tongue. Fish, for the reason stated, have this part but do not have it clearly articulated. Since the perception in the flavors exists for the sake of nourishment, they have the tongue-like part, but not alike throughout, rather chiefly at the tip. For this reason, in fish this alone is marked off.
61| [section 10] All animals have a desire for food, as having perception of the pleasure that comes from food; for desire is desire of the pleasant. But the part by which they perceive food is not the same in all: in some it is detached, in others attached — in those, that is, which have no function of voice — and in some it is hard, in others soft or fleshy. That is why in the soft-shelled crustaceans, such as crayfish and the like, there is something of this kind inside the mouth, [section 11] and likewise in the cephalopods, such as cuttlefish and octopuses. Of insects, some have this sort of part inside, as the ant tribe does, and so too do many of the testaceans; others have it outside, like a sting, spongy in nature and hollow, so that with this same part they both taste and draw up their food. This is clear in the case of flies and bees and all such creatures, and further in some of the testaceans; for in purple-shellfish this part has such power that they bore right through the shell even of conches — for example the shells of the whelks with which they are baited. Further, gadflies and horseflies, some of which pierce the skins of