Aristotle · a new plain-English translation from the original language
1| Why is it that, when a wound occurs repeatedly in the same place, the scar becomes black? Is it because every wound, once it has formed, is weak, and the more often it recurs the weaker it becomes; and what is weak is chilled and full of moisture? That is why it also appears black, since large wounds and long-standing ones have black scars. And to receive a wound many times is nothing other than having a wound for a long time. Why do we apply metal cups to bruises? Is it because, when we are struck, the place becomes chilled, and the heat withdraws? So the cup, being applied while the bronze is cold, prevents the heat from escaping. Why do hairs not grow on scars? Is it because the pores from which hairs grow are blocked up, and are displaced? Why do blows produce swelling and discoloration? Is it because, in that place, the fluids are forced apart, and, striking against the neighboring places, rebound back again and are drawn together by the cohesion of the fluids? And if some small veins are also torn, the gathering becomes suffused with blood. X. Summary of Natural Problems Why do some animals cough while others do not — man, for instance, coughs, but the ox does not? Is it because in most animals the residue turns off into something else, but in man it turns here? Or is it because man has the largest and moistest brain, and coughing arises from phlegm running down.
2| Why does blood flow from the nostrils in man alone among animals? Is it because he has the largest and moistest brain, from which the veins, filled with the residue, send out a flow through the passages? For diseased blood becomes thinner than pure blood, and this is blood mixed with the residues of the brain, and it is like serum. Why are some animals fat beneath the flesh, others fat throughout the flesh, and others fat in both ways? Is it that in those whose flesh is dense, the moisture is drawn together between the skin and the flesh, because [the skin] by nature stands apart from it — and this moisture, when concocted, becomes fat? But those that have looser flesh, with the skin lying close against it, become fat throughout the flesh. And those in both conditions grow fat in both ways. Why do children and women have vitiligo less than men, and among women the older women more? Is it because vitiligo is an escape of breath, and children's bodies are not well-vented but dense, and women's bodies less so than men's — for the breath turns instead into the menstrual discharge; and the smoothness of the skin shows the density of the flesh? But the bodies of older men and of old women are well-vented; for they alone, like old buildings, have the fitting-together of their parts loosened.
3| Why does man alone contract vitiligo? Is it because he is the thinnest-skinned of animals, and at the same time the most full of breath? A sign of this is that vitiligo occurs most, and first, in the thinnest-skinned parts. Or is it for these reasons, and also because he alone among animals turns gray? For in vitiligo the hairs turn gray, so that it is impossible for whatever does not turn gray to contract vitiligo. Why do goats and sheep, though they do not have the largest bodies, yield the most milk when milked, while man and the ox yield less in proportion? Is it because in the others what is left over is spent on the body, but in sheep and goats the whole surplus of the residue becomes milk? Or is it because they bear more young than the large animals, so that they draw off more residue because they nourish more offspring? Or is it that, because of the weakness of their bodies, more residue is produced in them while they are pregnant, and milk comes from the residue? Why do some animals, when they change their water, change their color too and become like the creatures there — goats, for instance — while others do not, man for instance? And in general, why do some change while others do not — the raven, for instance, does not change? Is it that those whose nature does not master the moisture, as with birds (which is also why they have no bladder), do not change? And why is it not the animals themselves but their offspring that change? Is it because the young are weaker than those that begot them?
4| Why are males generally larger than females? Is it because they are hotter, and heat promotes growth? Or because they are whole, while the females are stunted? Or because males reach completion over a long time, and females in a short time? Why do some animals bear young quickly, while others have a long gestation? Is it because the longer-lived are by nature slower to reach completion? And the long-lived are slow to give birth. Not, however, the longest-lived of all — the horse, for instance, is slower to give birth than man, yet shorter-lived. The cause of this is the hardness of its womb; for just as dry earth does not quickly bring things to maturity, so too the womb of the horse. Why do the offspring of the other animals resemble their parents' natures more than human offspring do? Is it because man's soul is affected in many different ways during intercourse, and according to how the father and the mother are disposed at the time, so too the offspring turn out varied? But most of the other animals are directed toward this one thing alone. Further, for the most part it is not fulfilled on account of this desire. Why are white men and horses generally gray-eyed? Is it because, there being three colors for eyes — black, goat-eyed, and gray — the color of the eye follows the color of the body, and this color, in their case, is grayness.
5| For what cause do dwarves come about? And still more generally, why are some animals altogether large, others small? This must be examined as follows. There are two causes: either place or nourishment. Place, if it is cramped; nourishment, if it is scanty — just as people try to make animals small even after they have already been born, for instance those who raise puppies inside quail-cages. Now those for whom place is the cause become pygmy-like. For they come to have breadths and [the] lengths corresponding to the size of their parents, yet are altogether small. The cause of this is that, because of the narrowness of the place, straight lines, being bent together, become curved. So just as figures painted on tavern signs are small, yet appear to have breadth and depth, the same thing happens with pygmies too. But those who become stunted through lack of nourishment turn out to have childlike limbs as well. And one can see some that are very small indeed, yet well-proportioned, like Maltese lap-dogs. The cause is that in this case it is nature, not place, that produces the effect.
6| Why do some animals come to be from one another, while others come to be from certain things combining, in the same way that their original generation once came about for them — just as those who discourse about nature say that the original generation of animals also came about because of the changes and shifts of the cosmos and the universe being so great; and if it is to happen again now, must not motions of that kind occur once more? For the beginning of every task is the greatest part of it, since it is half the whole. And seed is a beginning. Now for the small animals that do not come to be from one another, the cause of their coming to be just as they were generated at the start is the smallness of their seed; for the beginning of a smaller thing is also smaller. So that even the changes affecting such a creature are enough to generate seed for it, which is in fact what happens — for they come to be especially during changes. But the larger animals need a greater change as well. Why are some animals prolific, the pig, the dog, the hare, for instance, while others are not, man and the lion for instance? Is it because the former have many wombs and compartments, which desire to be filled and into which the seed is divided, while the latter have the opposite?
7| Why does a human being have the smallest distance between the eyes of all animals, in proportion to size? Is it because a human is most in accordance with nature among the others, and perception is by nature directed forward? For the direction in which motion occurs is the direction one must look ahead toward. And the greater the distance between the eyes, the more the lines of sight will fall to the side. If, then, one must be constituted according to nature, the distance ought to be as small as possible; for in this way one will travel forward most directly. Further, in the other animals, since they do not have hands, they are forced to look sideways as well. That is why their eyes are set farther apart, most of all in sheep, because of their proceeding on their way most of all with the head bent down. Why is it that some of the other animals do not have wet dreams at all, and others only rarely? Is it because none of them lies on its back, and nothing that does not lie on its back has a wet dream? Or is it that the other animals do not dream in the same way, while a wet dream occurs together with imagination? Why do some animals move the head, while others do not? Is it because some do not have a neck? That is why these do not move the head.
8| Why does a human being sneeze more than any other animal? Is it because he has wide passages through which breath and smell enter? For when these are filled with breath, sneezing occurs. That his passages are wide is shown by the fact that he has the weakest sense of smell of all the animals; for the finer passages give the more exact perception. If, then, into the wide passages the moisture enters in greater quantity and more often — the moisture whose turning into breath produces the sneeze — and humans have such passages more than any other animal, then it stands to reason they would sneeze most often. Or is it because their nostrils are shortest in length, so that the moisture once heated can quickly turn into breath? In the other animals, because of the length, it cools again first. Why does no animal have a fatty tongue? Is it because the fatty is dense, while the tongue is by nature porous, so that it may discern flavors? Why do females urinate with a straining effort, but males do not? Is it because the bladder of females lies farther off, both in depth and in length? For between them the womb lies between the seat and the bladder. So what is expelled needs more force, precisely because of the distance from the womb; and it is forced out by straining together with the breath.
9| Why do all animals that do not fly shed their winter hair, except the pig? For the dog sheds, and so does the ox. Is it because the pig is the hottest of animals, and its hairs grow out of heat? For the oily is of that character. In the case of the others, either the hairs fall out because the moisture is chilled, or because the animal's own heat is unable to concoct the nourishment; but because the pig's moisture within it undergoes nothing of that sort — since its nourishment is well concocted — it does not shed its hairs. For whenever the cause of shedding is present, richness of fat is sufficient to prevent it. Sheep and humans, because of the quantity and density of their hair, are unaffected: for the cold does not penetrate to depth, so as either to freeze the moisture or to prevent the heat from concocting it.
10| Why do the hairs of sheep grow back softer when plucked out, but those of humans harder? Is it because the hairs of sheep grow from the surface? That is why they are also pulled out without pain, since the root of their nourishment remains undestroyed, being in the flesh. Now the residues, once the follicles are opened, evaporate the more, while the wool takes its own proper nourishment from the flesh; and flesh is nourished by things soft and sweet. But the hairs of humans, growing from a depth, are pulled out by force and with pain. This is clear: for they draw up blood with them. So when the spot is wounded it happens also to scar over. That is why in the end this happens to those who pluck their hair; and as long as hairs continue to grow back, they grow back hard, because all the nourishing part of the flesh has been used up, and they are formed instead out of residues. Here is a sign: in all people who live toward the south the hairs are hard, because the external heat, penetrating to a depth, evaporates the well-concocted nourishment, while in those who live under the Bears the hairs are soft; for in these the blood and the sweet juices lie more toward the surface, which is also why they are of good complexion.
11| Why is it that the hairs of sheep become harder the longer they grow, while those of humans become softer? Is it because the hairs of sheep, having the kind of nourishment described, are less well nourished the farther they hang from their root, and the nourishment present in them is readily evaporated by heat because of its being easily concocted? And as they dry out they become drier, for the moist is soft. But the hairs of humans, though shorter, are more closely attached to their root; and they are concocted more in them because they are shorter, and being concocted makes the hair softer, since all concocted things are softer than unconcocted ones. For human hair grows out of a greater quantity of residue than sheep's hair does. Here is a sign: young sheep have softer wool than old ones. Why are humans and birds that are shaggy inclined to lust? Is it because they are hot and moist in nature, and both are needed for mating? For the hot excretes, and the moist is what is excreted. For the same reason lame men too are lustful; for their nourishment, little of it reaching down because of the disability of their legs, comes in quantity to the upper region and is combined into seed.
12| Why does a human being not have a mane? Is it because he has a beard, so that the nourishment which would go there, being of that kind of residue, goes instead to the jaws? Why do all animals have an even number of feet? Is it because motion is not possible unless something is at rest, unless the animal leaps? Since, then, motion in walking must necessarily consist of two things — motion and rest — these two are already an even number. And four-footed animals too, because they have more feet, are the same way: for they move two feet while the other two are at rest, and so too with six-footed animals; and the rest likewise have two more: of these, one is in motion, the other at rest.
13| Why is it that in horses and donkeys hairs grow out of scars, but not in humans? Is it because in the other animals the skin is part of the flesh, while in a human being it is, as it were, an affection of the flesh? For in them it seems that what is chilled at the surface becomes more solid, just as with boiled flour the substance called "the crust." Since, then, that too is boiled flour, what is called skin in a human being would likewise be flesh; and when a human is wounded or chafed, it happens that the flesh becomes dense. That is why, once the surface flesh has been altered, the wounds do not take on the same nature as they had from birth; and it is no strange thing that, once it has been altered, nothing further grows from it, just as with what are called foxes' manges — for these too are destructions and alterations of the surface flesh. But in beasts of burden, when they are chafed and then healed again, the diseased parts of the body are filled back in, being the same in kind but weaker than they were originally. And since the skin too is a part of them, hairs would form and grow (for hairs grow out of skin), but they grow white because the skin has become weaker than it was originally, and white hair is the weakest kind of hair.
14| Why is it that in other animals twins survive equally well whether one is female and the other male, but not in humans? Is it because in man twins are weakest of all, since man normally bears only one at a time? And for twins to occur, one female and one male, is contrary to nature in humans, so that what is most contrary to nature is also the weakest. Why is it that in horses and donkeys hair grows back over scars, but not in humans? Is it because the scar prevents it, either through its density or because it destroys the nourishment? In humans it prevents growth completely, on account of the weakness of human hair, whereas in horses it did not prevent it, but only impaired it. Why do animals have an even number of feet? Is it because in everything that moves, something must be at rest, and if the feet were odd in number this could not happen — for it was by the correspondence of the feet in opposite pairs that motion occurred. Why do animals sleep for a shorter time than they are awake, yet not continuously? Is it because not all of the residue is concocted at once? Rather, whenever some of it has been concocted, the animal, being lightened, wakes up. And those animals wake more often in which the place that concocts the residue is cold; for it stops quickly, and often, and each cessation is a waking. And it is not plausible that this happens because sleep is pleasant, merely on the ground that it appears to be a rest. For not even in that case does rest take up more time than the activities in accordance with nature; just as, even though eating is more pleasant than not eating, animals nonetheless do not spend more time eating than fasting.
15| Why is it that some animals follow their parents immediately, while others do so late, or with difficulty, or never — for example man? Is it because some quickly acquire the ability to recognize, while others acquire it late? And some are without perception of what benefits them, while others have such perception. So whichever animals have both of these — I mean both perception of what benefits them and completion of the body — follow their parents, while those that lack either one do not do this; for both being able to move and being able to perceive are required. Why does leukē, white blotching of the skin, not occur in other animals? Is it because in other animals it is a disease, whereas in humans it is natural for their skins and hairs to become mottled white? But still one might raise the difficulty of why it does not occur later in life instead, since the mottling is present from birth. Or is it because the skins of other animals are hard, while man is by nature the thinnest-skinned of all? And leukē is a discharge of breath, which in other animals is prevented from escaping the skin because of its density. Why is it that in leukē gray hairs occur, but where there are gray hairs, leukē does not always occur? Is it because hairs come from the skin, and grayness is a kind of decay of the hairs? So whenever the skin is affected, the hair that grows from it must be affected as well; but when the hair is affected, the skin need not be.
16| Why is it that some animals are fierce after giving birth — for example the dog and the pig — while others show no clear sign of it, for example woman and sheep? Is it because those that are full of residue are gentle, since in giving birth what was distressing them departs? But in those in which the removal comes from parts that were in good condition, (text breaks off) ...so that leanness produces the anger through its effect on the bodily state — just as hens are not fierce after laying, but while brooding, because of their fasting.
17| Why do eunuchs change toward the female in other respects when castrated — for they also acquire a female voice, both in pitch and in inarticulateness, and change so completely, just as castrated animals do among the other creatures — but bulls and rams, on the contrary, change in the growth of their horns, because the females of these animals are the opposite of the males in that respect? Hence some animals, when castrated, get larger horns, others smaller. But in size alone do eunuchs change toward the male, for they become larger; and this is a mark of the male, since females are smaller than males. Or is this too not a change toward the male, but toward the female? For it is not a change in every dimension, but only in length, whereas the male grows in breadth and depth as well, since that is when growth is complete. Further, as the female stands to the male, so within the female herself the maiden stands to the woman; for the one is already mature, the other not. So eunuchs change into the condition of these maidens, since their growth is in length. Hence Homer rightly says, "and height did holy Artemis give," as though, because of her own virginity, she — having that quality herself — was able to give it. Eunuchs, then, do not change toward the male in point of size, since they do not change toward the complete state; but eunuchs do gain increase in length as their one kind of size.
18| Why do eunuchs either not contract sciatica at all, or contract it less? Is it because in castration they change their nature into that of the barren? Such are the child and the woman, neither of whom contracts sciatica, except rarely a woman. Why does man emit many sounds, more than other animals, while other animals emit one, even though they do not differ within their own species? And man too has one voice, but many dialects. Why is this dialect different among humans, but not among other animals? Is it because humans utter many letters, while of the other animals some utter none, and some two or three of the consonants? And these, together with the vowels, produce a dialect. But speech is not simply signifying by voice, but by its affections — not merely that the animal is in pain or rejoices. The letters are affections of the voice. Children and beasts alike show this, for children too do not yet utter the letters. Why is man alone among the other animals subject to stammering? Is it because he is also subject to being mute, and stammering is a kind of muteness? But then again, in the stammerer this part is not even completely formed. Or is it because man has a greater share in reason, while the other animals have a greater share in mere voice? And stammering, despite its name, is not a weakness of voice, but rather an inability to run through a word as a single whole, or to run through it continuously.
19| Why is man born lame from birth more than the other animals? Is it because the legs of the other animals are strong? For four-footed animals and birds have legs that are bony and sinewy, while humans have fleshy ones; so because of this softness they are more quickly maimed in moving. Or is it because man alone among animals has many different times of birth? For some are born at seven months, some at eight, some at ten. For the other animals there is a single time of completion, without delay; but for humans there is much time spent in the process of formation in the womb, so that, since they move about while still soft, their extremities are broken more, the longer the time is. Why do eunuchs have shins that are ulcerous and diseased? Is it because women too have this, and eunuchs are womanish? Or is this merely incidental, and the cause, even in the case of women, is that the heat rushes downward? The menstrual discharge shows this. That is also why neither eunuchs nor women become hairy there, on account of their great wetness.
20| Why is it that no animal gets bladder stones except man? Is it because in beasts of burden and animals with many claws, the passages of the bladder are wide? And whatever animals do not at first, but later, bear their young alive within themselves, such as some fish, none of these have a bladder; instead this kind of sediment is compressed into their belly, as also in birds, so that it quickly passes out through the anus. But man has a bladder, and a narrow neck relative to its size. Because he has this part, then, the earthy matter is compressed into the bladder (which is also why chamber pots are discolored by it), and because of the heat of the place it is concocted together and thickened further; and it remains and grows because of the narrowness of the urinary passage. For the earthy deposits, unable to pass out easily, turn back upon one another and become a stone. Why do beasts of burden not belch, nor cattle and horned animals, nor birds? Is it because of the dryness of their belly? For the moisture is quickly used up and filtered through; but when it remains in place and becomes gaseous, belching results. In maned animals, because of the length of the neck, the breath rushes downward instead, which is why they produce sound from below most of all. Birds and horned animals do neither of these. Nor do animals that chew the cud belch, because they have many stomachs and the part called the reticulum; so the breath's passage occurs through many chambers, both upward and downward, and the moisture is used up before it can be turned into gas and produce either a belch or a sound from below.
21| Why is it that whatever animals are tame also have a wild form, while whatever are wild are not all also found tame? For men too appear wild in some places, and dogs among the Indians, and horses, and elsewhere, but lions are never tame, nor leopards, nor vipers, nor many others. Is it because it is easier for something inferior both to come into being from the start and to change into that state? For nature is not perfected straightaway at the first, but only at the end, and it is hard work to hit the mark immediately. That is why even tame animals become wild at first, more than tame, for example a child or a man who eats anything and lives by spirit alone -- but such creatures are weaker. So just as it is with the works of craft, so it is also with the works of nature. For in the case of crafts too, everything produced is at first inferior, and inferior products are more numerous, be it a bed or a cloak or anything else. And whatever is fine, it is possible to find inferior examples of it as well, but whatever is inferior is not all also fine -- for example, if one examines the works of the ancient painters and sculptors: for there was never anywhere a serious painting or statue, but they were inferior. Likewise nature too makes everything inferior, and more numerous and more often, while the serious ones are fewer, and it cannot do everything.
22| The tame is better, the wild inferior. Nature, not in its state at the very beginning, but in that toward which, I suppose (text breaks off here), it more easily makes things serious and tame. But the opposite creatures either never, or only with difficulty, and in certain places and at certain times, or at a fixed moment, or at some point in a certain mixture of the whole, do all animals become tame. The same holds also for all plants: for whatever are tame also have a wild form, but not all can be tamed; yet all the same there are, in their own region, plants specially suited to many things, so that, neglected and wild, they grow better and tamer than those cultivated in another region. Why is it that in humans the navels become large, while in other animals they are not conspicuous? Is it because in the others, since it remains inside for a long time, it withers and is drawn straight, while the whole wound swells up, which is why some navels are even rather unsightly? But man comes out incomplete, so that his navels come out moist and full of blood. And that some animals come out complete while others come out incomplete is shown by this sign: the former are able to live at once, while human infants need care.
23| Why is it that some animals mate only once, others many times, and some at a particular season of the year, others whenever it happens, man always, while wild animals do not mate often, and the wild pig only once, the domestic pig often? Is it because of feeding, warmth, and exertion? For Aphrodite thrives on plenty. Again, the same animals bear young once in one place, more often in another: for example sheep in Magnesia and in Libya bear young twice. The cause is the long duration of gestation there; for an animal does not desire mating once it is satisfied, just as full animals do not desire food. And pregnant animals desire mating less, because their purging does not occur. Why is it that among men, those who have widely-spaced teeth are for the most part short-lived? Is it because this is a sign that the bone is dense, so that the brain, being weak, does not breathe well, and so, being moist by nature, quickly putrefies? For other things too putrefy when not moved and not allowed to give off vapor. That is also why man is the hairiest of animals on the head, and why the male is longer-lived than the female, because of the sutures. But one ought to examine the case in other animals as well. And why are those who have the line across the hand running all the way through longer-lived? Is it because jointless creatures are shortest-lived, as are moisture-dwelling creatures? And if jointless creatures are short-lived, clearly the jointed ones are the opposite. Such are those in which even the parts naturally without joints are most articulated; and the inner part of the hand is the least jointed part.
24| Why is man, alone or most of all among animals, subject to becoming distorted? Is it because he alone, or most of all, is affected while still an infant, which is when it happens to all creatures to become distorted? Why is man affected by smoke more than any other animal? Is it because he weeps most of all, and being affected by smoke goes together with weeping? Why does a horse take pleasure in and desire a horse, and man a man, and in general do kindred creatures desire their kindred and their likes? For it is surely not for the same reason that every animal is fine, and desire is desire of the fine. For then the fine ought to be more pleasant. But as things are, rather, not every beauty is pleasant -- the fine (text corrupt here) and the pleasant. Nor is pleasure, or the fine's being pleasant, the same for everyone; for example, eating or drinking is more pleasant for one, and sex for another. Now why each creature, when mating with its own kind, has intercourse most fully and most pleasantly is a different problem; but that this partner is also the finest is not true. Rather, we suppose that what is pleasant for intercourse is fine, because, desiring it, we take pleasure in looking at it. And yet the same holds for the other desires as well: for the thirsty see a drink as more pleasant to look at. So whatever is fine with a view to some particular need, the thing we desire most, this seems to be most pleasant, while what is fine in its own right is no longer so. Here is a sign of this: for men too seem to us to be fine, when we look at them with a view to intercourse. Is it, then, in such a way that we also take more pleasure in looking at them than at things meant for intercourse? Nothing at all prevents this, if we should happen not to be desiring them. In the same way a drink looks finer too: for if we should happen to be thirsty, we shall see it as more pleasant.
25| Why is it that in man the front parts of the body are hairier than the back, while in four-footed animals it is the back parts that are hairier? Is it because all two-footed animals have hairier front parts? For birds are disposed in the same way as men. Or is it because nature always tends to cover the weaker parts more, and each part is weak in some particular way? Now in all four-footed animals the back parts are weaker than the front because of their position: for they are more liable to be affected by cold and heat. But in man the front parts are the weaker, and have suffered the same treatment.
26| Why does man sneeze more than any other animal? Is it because he also gets catarrh most? The cause of this is that, the hot element being around the heart and naturally tending to move upward, in the other animals its natural motion is toward the shoulders, and from there, splitting off by reflection, part of it moves toward the neck and head, part toward the spine and loins, because all these lie on the same straight line, alongside the base of the body. As the body moves in this way, it distributes the fluids evenly into these parts as well; for fluids follow the heat. That is why four-footed animals do not get much catarrh, nor do they sneeze; for sneezing is either a rush of gathered breath, when fluids are evaporating from the body more than usual, or a rush of unconcocted fluids. That is why it occurs before catarrhs, which do not happen to the other animals, because in them the motion of the heat is leveled out to front and back alike. But since man's base stands upright, like plants, it turns out that the motion of the heat toward the head is greatest and most vigorous. And moving there, it rarefies and heats the passages around the head.
27| Being in this state, they become more receptive of fluids than the passages below the heart are. So whenever it happens that they become moister than they should be and are chilled, the heat coming from outside, having nourishment and being drawn together within, grows; and as it grows it moves toward the head and the passages in it. The fluids, following along into these passages, being thin and unconcocted, fill them up and produce catarrhs, and likewise sneezes. For at the onset of catarrhs the heat, being carried up ahead of the fluid and turning the passages into breath, produces sneezes both by the expulsion of the breath and by the prior upward carrying of the fluids, which are thin and sharp. That is why, along with the sneezes of a catarrh, watery discharge is also blown out through the nose. But once all these have set out, the adjoining fluids, being in the same affected state, settle upon them and block up the passages around the head and nose; for as they become bulkier and stretch the passages, they cause the pains around the head. A sign of this is that no breath is released either outward or through them. That is why people with catarrh neither sneeze nor smell. Those who sneeze without catarrh come about through the same causes, but starting from small and slight beginnings.
28| So the fluids, gathered together with the heat and turned into vapor by it because there is little of them, fall in along the nostrils. The violence of the motion produces the noise of the breath no less than its quantity does. For when the heat is carried straight up against the brain and strikes upon it, it is reflected toward the nostrils, because the passages there stretch outward from the brain. Since, then, the motion of the breath toward the nostrils that results from this reflection is contrary to nature, it turns out to be violent; that is why it produces noises. Among the other animals, birds are the ones most subject to catarrh, because they are most similar in shape to man; but they suffer it less than man does, because most of them hold their head down, since their feeding is from the ground. Why are sea animals larger and better-nourished than land animals? Is it because the sun, by consuming what surrounds the earth, takes away its nourishment? That is why enclosed places too are better for nourishment. Sea animals, then, are free from all this. Why is it that the other animals take dry food more often than moist, while man takes moist more often than dry? Is it because man is by nature the hottest of animals? He therefore needs the most cooling.
29| Why do eunuchs not go bald? Is it because they have much brain? This happens to them because they do not have intercourse with women; for semen proceeds from the brain, down through the spine. This is also, it seems, why castrated oxen have large horns once they are castrated. The same cause seems to explain why women and children are not bald. Why can some animals nourish themselves on their own immediately after birth, while others cannot? Is it those that are shorter-lived among the ones capable of memory? That is why all such also die sooner. Why is it that man produces a moister excretion than dry, while horses and donkeys produce a drier one? Is it because these animals use more dry food, while man uses moist food rather than dry? All excretion comes from food, and more excretion from more food. So some animals use more moist food, others more dry, because some animals are by nature dry, others moist. Those that are by nature dry desire the moist more, for they are more lacking in it, and those that are by nature moist desire the dry more; for they are more lacking in that.
30| Why are birds and men, and the animals that are courageous, harder in body? Is it because spirit goes with heat? For fear is a chilling. So whatever animals have hot blood are both courageous and spirited; and blood is nourishment. And whatever growing things are watered with heat all become harder. Why do the small four-footed animals give birth to monstrosities more than the large ones do, while man, and the large animals such as horses and donkeys, do so less? Is it because these small ones are prolific — dogs, pigs, goats, and sheep — much more than the large animals, whereas of the large ones some bear only a single offspring altogether, and most of the others generally do so too? Monstrosities occur when the seeds overlap one another and become mixed together, either at the emission of the semen or in the mixing that takes place in the womb of the female. That is why birds too produce them; for they lay twin eggs. Monstrosities arise from twins whose yolk is not divided by the membrane.
31| Why is the head of humans hairier than the rest of the body, and disproportionately so, while in the other animals it is the opposite? Is it because, among the others too, some expend the excess of their nourishment into teeth, some into horns, some into hair? Those that expend it into horns have a less hairy head, since it has been used up there; those that expend it into teeth have more hair than the horned animals do, for they have a mane, but less than animals of this other kind, such as birds. For these latter also have the human pattern: what in those other animals is distributed in many places on account of its quantity, this in man is expended entirely into the head; for he has nothing else into which to expend it, nor is there so much of it that it must go everywhere. Why does man alone among animals go gray? Is it because most animals shed their hair every year, such as the horse and the ox, while some do not shed it but are short-lived, such as the sheep and others — these have hair that, as it were, does not age, and so does not go gray either? Man, however, neither sheds his hair, and is long-lived, so that with time it goes gray. Why are those in whom the parts below the navel are larger than those toward the chest short-lived and weak? Is it because the belly is cold on account of its smallness, so that it is not good at concoction but tends to produce residue? Such people are sickly.
32| Why do some animals come to be not only from each other but also spontaneously, while others come only from each other, for example man and horse? Is it, if for no other reason, because in some the time of generation is short, so that the breeding season does not extend beyond it, and it is possible for generation to occur within the change of the seasons, while in others the generation takes much longer — for they take a year or ten months — so that it is necessary (text breaks off) to come to be, or to come to be from each other. Why are the teeth of Ethiopians white, and whiter than other people's, but their nails not likewise? Is it that the nails are as they are because their skin too is black, and blacker than that of other people, and the nails grow out of the skin? But why are the teeth white? Is it because whatever the sun draws the moisture out of, without staining it, turns white — as with wax too? So the skin is stained, but the teeth are not stained; rather the moisture evaporates out of them because of the heat. Why do some animals die at once or quickly when the head is removed, while others do not? Is this what happens to whatever is bloodless and needs little nourishment? For such animals do not need nourishment quickly, nor is heat poured into them together with the moisture, without which sanguineous animals cannot live. But for these other animals it is possible to live without it; for they can live much more without breathing. The cause has been stated elsewhere.