Parts of Animals · Book IV

Aristotle · a new plain-English translation from the original language

1| [section 2] All these animals have rennet because of the thickness of their milk; the single-stomached animals do not have it, for the milk of single-stomached animals is thin. Hence the milk of the horned animals curdles, while that of the hornless animals does not curdle. [section 3] The hare gets rennet from grazing on juicy grass; for this kind of juice causes the milk to curdle in the stomach for the young. As for why, among the many-stomached animals, the rennet occurs in the manyplies, this has been discussed in the Problems. Book 4. [section 1] Chapter 1. The parts around the viscera and the stomach, and each of the parts mentioned, are arranged in the same way in the four-footed animals that are egg-laying, and in the footless ones, such as snakes. For the nature of snakes is akin to these; it is like a long, footless lizard. [section 2] These and fish are all very similar to one another, except that the former have lungs because they walk on land, while the latter do not have lungs but gills instead. Fish have no bladder, nor does any of these other animals, except the tortoise; for the liquid is turned into the

2| scales, since these animals drink little, because of the bloodlessness of the lung, just as in birds it is turned into the feathers. [section 3] The residue whitens in all of these too, as in birds; and so, in the animals that have a bladder, once the residue has passed out, a salty, earthy sediment settles in the vessels; for the sweet and drinkable part is used up, because of its lightness, into the flesh. [section 4] Among snakes, vipers have the same difference from the rest that, among fish, the cartilaginous fish have from the rest; for both the cartilaginous fish and the vipers bear their young alive outside the body, though they first lay eggs within themselves. All such animals are single-stomached, like the other animals with both kinds of teeth; and they have altogether small viscera, like the other animals that lack a bladder. [section 5] Snakes, because of the shape of their body, which is long and narrow, have the shapes of their viscera long and unlike those of other animals for this same reason, because their shapes have been molded, as if in a mold, on account of their place. [section 6] All the blooded animals have the caul, the mesentery, and the structures concerning the nature of the intestines, and further the diaphragm and the heart; and all except fish have a lung and a windpipe. And all that have them have the position of the windpipe and the gullet arranged in the same way, for the reasons stated before.

3| [section 1] Chapter 2. Most of the blooded animals also have gall, some on the liver, others suspended near the intestines, since its nature comes no less from the lower stomach; this is clearest in the case of fish. For all of these have it, and most of them have it near the intestines, while some have it woven along the whole length of the intestine, as in the amia; and most snakes have it in the same way. Hence those who say that the nature of gall exists for the sake of some kind of perception are not speaking correctly. For they say it exists so that, by biting the part of the soul around the liver, it may cause distress, and by being dissolved, it may produce a gracious mood. For some animals have no gall at all, such as the horse, the mule, the donkey, the deer, and the roe deer. [section 2] Nor does the camel have it as a separate organ, but rather has small gall-like veins. Nor does the seal have gall, nor, among sea creatures, the dolphin. [section 3] And within the same kinds, some are found to have it and others not, as in the case of mice. Man too belongs to this class; for some are found to have gall on the liver, and others not to have it. For this reason a dispute also arises concerning the whole kind; for those who happen to have encountered animals either way suppose, concerning all of them, that all have it.

4| [section 4] The same thing happens also with sheep and goats; for most of these have gall, but in some places so much that the excess seems monstrous, as in Naxos, while in other places they have none, as in a certain district of Chalcis in Euboea. Further, as has been said, the gall of fish is suspended far from the liver. [section 5] The followers of Anaxagoras do not seem to be right in supposing that gall is the cause of acute diseases, on the ground that, when it overflows, it sprinkles out onto the lung and the veins and the ribs. For in nearly all cases where these disease-conditions occur, the animals do not have gall, and this would become evident in dissections; further, the quantity present in illnesses and the quantity that supposedly overflows are not comparable. [section 6] But it seems that gall, just as the residue or waste-product that forms elsewhere in the body, is likewise the gall on the liver: it is a residue and does not exist for the sake of anything, just as the sediment in the stomach and in the intestines is not for the sake of anything. [section 7]

5| 7 Nature, then, sometimes puts even residues to good use, but this does not mean we must look for the sake-of-what in every case; rather, when certain things exist for a reason, many other things follow from them of necessity. [section 8] 8 So in those animals in which the constitution of the liver is healthy and the nature of the blood that is secreted into it is sweet, these either have no bile on the liver at all, or have it in some small veins only, or have it in some places but not others. This is why the livers of animals without bile are, generally speaking, well-colored and sweet, and in animals that do have bile, the part of the liver beneath the bile is the sweetest. [section 9] 9 In animals whose liver forms from less pure blood, this — the bile — is the residue produced. For a residue must be the opposite of nourishment, and the bitter the opposite of the sweet, and healthy blood is sweet. [section 10] 10 It is clear, then, that bile does not exist for the sake of anything, but is a purgation. This is why the most graceful thing said among the ancients is the claim that not having bile is the cause of living a longer time — a claim made by looking at the solid-hoofed animals and the deer; for these are without bile and live a long time.

6| [section 11] 11 Further, there are also animals not observed by those thinkers to be without bile, such as the dolphin and the camel, and these too happen to be long-lived. For it is reasonable that the nature of the liver, being of vital importance and necessary to all blooded animals, should be a cause, by being of a certain sort, of living a shorter or a longer time. [section 12] 12 And it is in accordance with reason that this organ alone has such a residue, and none of the others does. For no such fluid can come near the heart (it admits no violent affection), and none of the other internal organs is necessary to animals, but the liver alone is; and this is why this residue occurs about the liver alone. [section 13] It is also absurd not to hold everywhere that wherever one sees phlegm or the sediment of the belly, it is a residue, and likewise, clearly, bile as well, and not to make a distinction based on location. [section 1] We have now spoken of bile, and of the reason why some animals have it and some do not; it remains to speak of the mesentery and the omentum, for these are located in this same region and go together with these parts. The omentum is a membrane which, in animals that have suet, is suety, and in those that have fat, is fatty; and we have already said what each of these is.

7| [section 2] 2 The omentum is attached, alike in single-stomached and many-stomached animals, from the middle of the stomach along what looks like a seam, as described. It covers the rest of the stomach and the mass of the intestines alike in blooded animals, both in land animals and in aquatic ones. [section 3] 3 The formation of this part comes about of necessity in the following way: when a mixture of dry and moist is heated, its outermost part always becomes skin-like and membranous, and this region is full of nourishment of that sort. [section 4] 4 Further, because of the density of the membrane, what filters through from the blood-like nourishment must be fatty (for this is the finest part), and because of the heat in that region, as it is concocted, it becomes, instead of a fleshy and blood-like constitution, suet and fat. [section 5] 5 The formation of the omentum, then, comes about on this account; but nature puts it to further use for the good digestion of food, so that animals may digest their food more easily and more quickly; for what is hot is capable of digesting, and what is fatty is hot, and the omentum is fatty. And this is why it is attached from the middle of the

8| stomach: because the part next to that region helps concoct along with the adjoining liver. This concludes what we have said about the omentum. [section 1] 4 What is called the mesentery is a membrane, stretching continuously from the extent of the intestines to the great vein and the aorta, and it is full of many dense veins that stretch from the intestines to both the great vein and the aorta. [section 2] 2 We shall find that its formation comes about of necessity, as with the other parts; but the reason why it exists in blooded animals becomes clear on examination. For since it is necessary that animals take in nourishment from outside, and that from this in turn the final nourishment be produced, from which it is now distributed to the parts (this is nameless in bloodless animals, but is called blood in blooded ones), there must be something through which the nourishment will travel from the stomach into the veins, as though through roots. [section 3] 3 Now plants have their roots in the earth (for it is from there that they take their nourishment), but for animals the stomach and the power of the intestines are the earth from which they must take their nourishment; and this is why the mesentery exists — having, as it were, roots in the veins that run through it.

9| [section 4] 4 We have now said for the sake of what the mesentery exists; the manner in which it takes in the nourishment, and how what is distributed into the veins enters through the veins from the incoming nourishment into these parts, will be spoken of in the treatise on the generation of animals and on nourishment. [section 5] 5 We have now said how the blooded animals stand with respect to the parts we have distinguished, and for what reasons; as for the parts that contribute to generation, in which the female is thought to differ from the male, this too follows on and remains from what has been said; but since we must speak about generation, it is fitting to go through these matters as well in the treatise on that subject. [section 1] 5 The creatures called the cephalopods and the crustaceans differ greatly from the blooded animals in these respects; for straight off they do not have the whole nature of internal organs at all. And likewise none of the other bloodless creatures has them either. There remain two further kinds of bloodless creatures, the testaceans (shell-creatures) and the class of insects. For none of these has blood, because none of them is composed of that out of which the nature of the internal organs is formed, since this is itself an affection belonging to their substance; for the fact that some animals are blooded and others bloodless will be present in the account that defines their substance.

10| [section 2] 2 Further, none of that for the sake of which the blooded animals have internal organs will be present in these creatures; for they have neither veins nor a bladder, nor do they breathe, but it is only necessary for them to have the part analogous to the heart. For the perceptive part of the soul and the cause of life are present in some principle among the parts and of the body, in all animals alike. [section 3] 3 These creatures also have, of necessity, the parts concerned with nourishment, but the ways in which they have them differ because of the places in which they take their nourishment. The cephalopods have, around what is called the mouth, two teeth, and in the mouth, in place of a tongue, something fleshy by which they judge the pleasure found in what they eat. [section 4] 4 Likewise the crustaceans have, like these, the first pair of teeth and the fleshy part analogous to the tongue. Further, all the testaceans also have such a part, for the same reason as the blooded animals, for the perception of their food. Likewise too the insects: some have a protruding sucker at the mouth, as for example the class of bees and the class of flies, as has already been said; but those that are not front-stinging have such a part in the mouth, like that of the

11| the ant tribe and any other such creature. Some of these have teeth, though of a different sort, as in the tribe of ants and the tribe of bees; others do not, namely all those that take liquid food, [section 5] for many insects have their teeth not for the sake of food but for defense. Among the testaceans, some, as was said in the discussions at the beginning, have the so-called strong tongue, while whelks also have two teeth, like the crustaceans. In the cephalopods, after the mouth there is a long gullet, and adjoining this a crop such as birds have, then continuous with it a stomach, and adjoining this a simple intestine running to the outlet. [section 6] In cuttlefish and octopuses the parts around the stomach are alike both in shape and to the touch; but in the so-called calamary there are likewise two stomach-like receptacles, though the second is less crop-like, and they differ from those others in shape as well, because their whole body is composed of softer flesh.

12| [section 7] These creatures have their parts arranged in this way for the same cause as birds do; for none of these is able to grind its food smooth, and this is why the crop is placed before the stomach. For help and safety they have the so-called ink, attached within a membranous sac that has an outlet and an opening where they discharge it along the passage called the funnel, through which they also expel the residue of the stomach; this funnel is on their underside. [section 8] Now all the cephalopods have this part as peculiar to them, but the cuttlefish has it most of all and in greatest quantity; for whenever they are frightened and afraid, they make a screen in front of their body out of the blackness and murk of this liquid. [section 9] The calamaries and octopuses have the ink sac higher up, more toward the cuttlebone, while the cuttlefish has it lower, near the stomach; for it has more of it because it makes more use of it. This happens to it because its life is spent near the shore, and it has no other means of defense, whereas the octopus has its tentacles as useful, and also the change of color, which happens to it, like the discharge of ink, on account of timidity. The calamary alone of these lives out at sea. [section 10] So the cuttlefish has more of this ink than the others, and has it lower down because it has more; for it is easy to discharge it, and from far off, on account of having more. The ink comes about, just as in birds the white sediment on their residue is the earthy part, so too in these creatures the ink arises because they likewise have no bladder; for the most earthy matter is separated off into it, and in the cuttlefish it is most abundant because it has the most earthy matter.

13| [section 11] A sign that this is so is the cuttlebone itself; for the octopus does not have this, while the calamaries have one that is cartilaginous and thin. The cause why some lack it and others have it, and what sort each of these has, has been stated. Since these creatures are bloodless and for this reason chilled and prone to fear, just as in some animals, when they are afraid, the belly is disturbed, and in others residue flows from the bladder, so in these creatures too this happens of necessity, their discharging it out of timidity, just as with those who involuntarily urinate from the bladder; but nature at the same time makes use of this kind of residue for their help and safety. [section 12] The crustaceans too, both the lobster-like kinds and the crabs, have two front teeth, and between them the tongue-like flesh, as has been said before, and immediately adjoining the mouth a gullet small in proportion to the size of their bodies, the larger ones proportionally to the smaller; and adjoining this a stomach, upon which the lobsters and some of the crabs have other teeth, because the upper ones do not divide the food sufficiently; and from the stomach a simple intestine running straight to the outlet of the residue.

14| [section 13] Each of the testaceans also has these parts, some more distinctly articulated, others less so; in the larger kinds each of these is more clearly visible. Whelks have teeth that are hard and sharp, as has been said before, and between them fleshy matter similar to that in the cephalopods and crustaceans, and the proboscis, as has been said, lying between a sting and a tongue; adjoining the mouth is something like a bird's crop, and adjoining this a gullet; adjoining this is the stomach, in which is the so-called poppy, from which a continuous intestine begins, simple from its start at the poppy; for in all the testaceans this is the residue that seems most fit to be eaten. [section 14] The other spiral-shelled kinds have the same arrangement as the whelk, for example purple-shellfish and trumpet-shells. There are many genera and species of testaceans; some are spiral-shelled, as those just mentioned, others are two-shelled, others one-shelled. [section 15] In a way even the spiral-shelled kinds resemble the two-shelled; for all such creatures have, from birth, coverings over the exposed part of their flesh, as do the purple-shellfish, trumpet-shells, and nerites, and the whole tribe of that sort, for their protection. For where the shell does not project in front, it is easy for that part to be harmed by things striking it from outside.

15| [section 16] The one-shelled kinds are kept safe, since they are attached, by having their shell overhanging, and in a way become two-shelled by means of a borrowed screen, as with the so-called limpets; the two-shelled kinds, such as scallops and mussels, are protected by closing together; and the spiral-shelled kinds by this covering, becoming as it were two-shelled out of one-shelled. [section 17] The sea urchin of all these has the greatest protection; for its shell is roofed over on every side and fortified with spines. It has this peculiar to it among the testaceans, as has been said before. [section 18] The nature of the crustaceans and testaceans is constructed in a manner opposite to that of the cephalopods; for in the latter the fleshy part is outside, in the former it is inside, and the earthy part outside. The sea urchin has no fleshy part at all. Now all the other testaceans have, as has been said, a mouth and the tongue-like part and a stomach and an outlet for the residue, but they differ in position and in size. [section 19] The manner in which each of these is arranged should be studied both from the Researches on Animals and from the dissections; for some things must be made clear by argument, others rather by reference to the sight of them. The sea urchins and the tribe of the so-called sea-squirts have a peculiar arrangement among the testaceans.

16| [section 20] The sea urchins have five teeth, and between them the fleshy matter that is found in all the creatures mentioned, and adjoining this a gullet, and from this a stomach divided into many parts, as though the animal had many stomachs. For they are separate and full of residue, but they are all suspended from one gullet and end in one outlet for the residue. [section 21] Besides the stomach they have nothing fleshy, as has been said, but they have what are called eggs, several in number, each apart in its own membrane, and arranged in a circle from the mouth, certain black bodies scattered loosely about, which have no name. Since there are several genera (for the sea urchins are not all one species), all have these parts, but not all have the so-called eggs edible, and in those outside the surface-dwelling kinds they are altogether small. [section 22] In general this also holds true of the other testaceans as well; for their flesh is not equally edible in all of them, and the residue, the so-called poppy, is edible in some, not edible in others. In the spiral-shelled kinds this is located in the coil; in the one-shelled kinds, at the base, as in limpets; in the two-shelled kinds, near the hinge; and the so-called egg is on the right side, while on the other side is the outlet of the residue, in the two-shelled kinds.

17| [section 23] 22 It is not rightly called an "egg" by those who call it so; for this is, in the blooded animals, what fatness is when they are thriving. That is why it also occurs at those seasons of the year in which they thrive, in spring and in autumn; for in the cold and in the heat all the testaceans suffer, and cannot bear the extremes. [section 24] 24 A sign of this is what happens in the case of sea urchins: they have it as soon as they are born, and more at full moons — not because of feeding about, as some think, but because the nights are warmer on account of the moon's light. For being bloodless, they feel the cold badly and need warmth. That is why nearly everywhere they thrive more in summer, except those in the Euripus of Pyrrha; those thrive no less in winter. The cause is that they have a more abundant food supply then, since the fish leave those places at that season. [section 25] 25 All sea urchins have eggs equal in number to each other and odd in number: they have five, and just as many teeth and stomachs too. The cause is that the "egg," as has been said before, is not an egg but the animal's good nourishment. In oysters this occurs on one side only — what is called the egg.

18| And this same thing is what occurs in sea urchins as well. [section 26] 26 Since, then, the sea urchin is spherical, and not, as with the other testaceans, having one circle to its body while the sea urchin is not this way in one part and otherwise in another but is alike all round (for it is spherical), the egg too must necessarily be arranged in like fashion. For it is not the case, as with the others, that going round the circle it is unlike itself. For in all the others the head is in the middle, and such a part faces upward. [section 27] 27 But moreover the egg cannot form a continuous ring: for it does not in the others either, but only on one side of the circle. It is necessary, then — since this is common to all of them, while it is peculiar to the urchin that its body is spherical — that its eggs not be even in number. For if they were even, they would lie along a diameter, since they would need to correspond alike on this side and that, if they were even and diametrically placed; and being so arranged, the egg would occupy both sides of the circle. But this did not hold even in the other testaceans; for oysters and scallops have such a part on only one side of their circumference. It is necessary, then, that there be three or five, or some other odd number.

19| [section 28] 28 If, then, they had three, the intervals would be too far apart; if more than five, they would be continuous; and of these, the one is not better, the other is not possible. It is necessary, therefore, that they have five eggs. For the same cause, the stomach too is divided in this way, and the number of teeth is likewise this many. For each of the eggs, being as it were a body-part of the animal, must necessarily correspond to its manner of life, since growth proceeds from it. For if there were only one, it would either be far off in a small part, or would occupy the whole cavity, so that the urchin would be hard to move and its vessel would not fill with food; but there being five intervals, it is necessary that near each one the body be divided fivefold. [section 29] 29 For the same cause the number of teeth is also this many; for in this way nature would have given like correspondence to the parts mentioned. Why, then, the sea urchin has an odd number of eggs, and this many, has been stated. Why some urchins are altogether small and others large, the cause is that the latter are hotter by nature; for heat is more able to concoct the food, and this is why the ones not fit to eat are fuller of residue.

20| [section 30] 30 And the heat of their nature also makes them more mobile, so that they range about and do not remain fixed in place. A sign of this is that such urchins always have something on their spines, as if they were moving about frequently; for they use their spines as feet. [section 31] 31 The sea-squirts differ little in nature from plants, yet they are more alive than sponges; for the latter have altogether the capacity of a plant. For nature passes continuously from lifeless things to animals, through things that are alive but are not animals, so that each seems to differ very little from its neighbor because of how close they lie to one another. [section 32] 32 The sponge, then, as has been said, lives only so long as it is attached, and when detached it does not live, and in this it is exactly like the plants. But the things called sea-cucumbers and sea-lungs, and other such things in the sea, differ little from these, though detached: for they have no perception at all, but live as though they were detached plants. [section 33] 33 There are also some such things among the plants of the land, which both live and grow, some on other plants, some even when detached, such as the plant from Parnassus called by some the "rock-plant"; for this lives a long time hanging up on pegs.

21| [section 34] 34 And sometimes the sea-squirts too, and any other such kind, being attached, live in a way like a plant only, but by having something fleshy might seem to have some perception; and it is unclear which way this should be decided. This animal has two passages and one opening, by which it takes in the moisture for nourishment, and by which again it sends out the remaining fluid; for it has no residue that is apparent, as the other testaceans do. That is why this creature above all, and any other animal like it, may rightly be called plantlike; for none of the plants has residue either. Through the middle there is a thin partition, in which it is reasonable that the governing part of its life resides. [section 35] 35 Those which some call nettles and others call sea-anemones are not testaceans, but fall outside the divided genera, and this creature is ambivalent in its nature between plant and animal. For in detaching itself and falling upon its food, some of them are animal-like, and in perceiving what falls upon them; further, it uses the roughness of its body for its protection. But in being incomplete and quickly attaching itself to the rocks it resembles the genus of plants, and in having no residue that is evident, though it does have a mouth.

22| [section 36] 36 Similar to this is also the genus of the starfish; for this too, falling upon them, drains the juice out of many of the oysters, and also out of the detached ones among the animals mentioned, such as the mollusks and the crustaceans. The same account holds also concerning the testaceans. [section 37] 37 The parts concerned with nutrition, then, which must belong to all, are as has been described; but clearly there must also be, in these too, some part analogous to what belongs to the blooded animals with respect to the governing organ of the senses; for this must belong to all animals. In the mollusks this is a moist thing lying within a membrane, through which the gullet stretches toward the stomach, and it is attached more toward the underside, and is called by some the mytis. [section 38] 38 Such another part belongs also to the crustaceans, and that too is called mytis. This part is moist and fleshy at once, and through it, as has been said, the gullet stretches through the middle; for if it lay between this part and the underside, it would not be able to expand equally as the food entered, because of the hardness of the back.

23| [section 39] 39 In the mytis, the intestine lies outward, and the ink is next to the intestine, so that it may be as far as possible from the entrance, and the disagreeable part may be kept away from the better part and the source. That this part is analogous to the heart is shown by its position (for this is the same) and by the sweetness of the fluid, since it is concocted and blood-like. [section 40] 40 In the testaceans the ruling part of perception has the same character, but it is less evident. Still, in those that are stationary, midway between the part that receives nourishment and the part through which the discharge of seed or of residue is made; in those animals that also move about, always in the middle between right and left. [section 41] 41 In insects, the part that holds such a source, as was said in the first accounts, lies between the head and the cavity around the belly. In most of them this is one part, but in others it is several, as in the millipede-like and elongated ones; that is why they go on living when cut apart. For nature wishes, in all cases, to make only one such part, but being unable to, it makes it only one in actuality, though several in potentiality; and this is more evident in some than in others.

24| [section 42] The parts concerned with nourishment are not the same in all; rather they show much difference. For inside the mouth, some have what is called the sting, a sort of composite organ having the power of tongue and lips together; those that do not have the sting in front have, inside the teeth, a similar organ of perception. [section 43] Next to this, in all of them, is an intestine that is straight and simple as far as the exit of the residue; but in some this has a coil. 43 Others have a stomach after the mouth, and from the stomach the intestine runs coiled, so that those that are more voracious eaters and greater in their nature may have a receptacle for more nourishment. [section 44] The class of cicadas has, most of all these, a nature of its own; for it has one and the same part serving as mouth and tongue grown together, 44 through which, as if through a root, it takes in nourishment from moist things. [section 45] All insects, then, are creatures needing little nourishment, 45 not so much because of their smallness as because of their coldness (for what is hot both needs nourishment and concocts nourishment quickly, while what is cold needs little nourishment); and this is most true of all of the class of cicadas. For a sufficient nourishment for the body is the moisture that remains from their breath, just as with the ephemeral creatures (these occur around the Pontus), except that those live for the space of a single day, while these live for several days, though few.

25| [section 46] Now that we have spoken of the parts present within animals, 46 we must go back again to the remaining external parts. We must begin from what has just now been said, and not from the point at which we left off, so that, having spent less time on these, our account may have more leisure for the complete and blooded animals. [section 1] The insects, then, are not many-parted in number, 6 yet they do have differences from one another. All of them are many-footed, because, given the slowness and the coldness of their nature, having many feet makes their motion more effective for them; and those most chilled through because of their length are the most many-footed, as the class of millipedes. [section 2] 2 Further, because they have several sources, both their segmentations occur and they are many-footed accordingly. Those that have fewer feet are winged, to compensate for the deficiency of their feet. [section 3]

26| 3 Among the winged creatures themselves, those whose life is nomadic, and who must move from place to place for the sake of food, are four-winged and have a light bulk of body, as the bees and the creatures of the same kind as they; for they have two wings on each side of the body. Those of this kind that are small are two-winged, as the class of flies. Those that are small in size and settled in their manner of life are many-winged in the same way as bees, but have wing-cases over their wings, as the cockchafers and such insects, so that the power of the wings may be preserved; for since they are settled, they are more easily damaged than the ones that move about easily, and that is why they have a barrier placed before them. [section 4] 4 The wing of these is also undivided and stemless; for it is not a feather but a skin-like membrane, which of necessity stands off from the body because of dryness, once the fleshy part has cooled. [section 5] 5 They are segmented both because of the causes stated, and so that they may be preserved from harm by being able to bend up; for those of them that are elongated coil themselves together, and this could not happen to them if they were not segmented. Those of them that do not coil become harder instead, being compacted together at the incisions.

27| [section 6] 6 This becomes clear when one touches them, as in the case of the creatures called beetles; for when frightened they become motionless, and their body becomes hard. And it is necessary for them to be segmented; for this belongs to their very substance, the having of many sources, and in this respect they resemble plants. For just as plants, so these too are able to live when divided, except that these live on only for a while, whereas plants both become complete in nature and become two, or more in number, out of one. [section 7] Some insects also have stings for help against what does them harm. The sting is in front in some, behind in others; 7 in front, at the tongue; behind, at the tail. For just as, in elephants, the organ of perception for smells has come to be useful both for defense and for the use of food, so too in some insects the organ set at the tongue; for by this they both perceive their food and take it up and bring it to themselves. [section 8] Those of them that are not front-stinged have teeth, some for the sake of eating, 8 others for taking hold of and drawing in their food, as the ants and the whole class of bees. Those that are rear-stinged have the sting because they have spirit, as a weapon.

28| [section 9] Some have their stings within themselves, as the bees and the wasps, because they are winged. 9 For being thin, if they were outside they would be easily destroyed; and if the sting stood out as it does in scorpions, it would add weight. But scorpions, being ground-walkers and having a sting, must of necessity have the sting placed in this way, or else it would be of no use for defense. No two-winged creature is rear-stinged. [section 10] For it is because they are weak and small that they are two-winged; 10 for small creatures are adequately lifted by a smaller number of wings. And for this same reason they also have the sting in front; for being weak, they can barely strike with their front parts. But the many-winged creatures, because they are greater in their nature, have come to have more wings, and are strong in their hind parts. [section 11] 11 It is better, when it is possible, not to have the same organ serve dissimilar uses, but rather to have the defensive part be as sharp as possible, and the tongue-part spongy and suited for drawing in food. For wherever it is possible to use two instruments for two functions without one hindering the other, nature is not accustomed to make one thing serve both, the way bronze-working does, for the sake of cheapness, with its combined spit-and-lampstand; but where it is not possible, it makes one and the same thing serve for several functions.

29| [section 12] 12 Some of these have larger front feet than the rest, so that—since, being hard-eyed, they do not have precise vision—they can clean off with their front legs whatever falls on them; and flies and the bee-like animals are visibly seen doing just this, for they are constantly scraping with their front legs. The hind legs are larger than the middle ones, both for walking and so that they may lift off more easily from the ground when flying up. [section 13] 13 In the jumping insects this is even more evident, for example locusts and the flea family: for whenever, having bent their legs, they extend them again, they must be lifted from the ground. Locusts have their rudder-like legs not in front but only behind, for the bend must be turned inward, and none of the front limbs is of this kind. All such creatures are six-footed, counting the leaping parts. [section 1] 7 The body of the testaceans is not made of many parts. The cause of this is that their nature is stationary; for animals capable of movement must necessarily have more parts, because they have actions to perform, and what shares in more kinds of motion needs more organs.

30| [section 2] Of these, some are entirely motionless, others share in a small amount of motion; but nature has provided the hardness of their shells for their preservation. Some of them are single-shelled, some double-shelled, and some spiral-shaped, as has been said before; and of these, some have a coil, for example whelks, while others are simply spherical, like the sea-urchin family. [section 3] And of the double-shelled kinds, some open, for example scallops and mussels (for they are joined together on one side, so that they open and close on the other), while others are fused together on both sides, for example the razor-shell family. [section 4] All the testaceans, like plants, have their head below. The cause of this is that they take in nourishment from below, just as plants do with their roots. It follows, then, that what is below in them corresponds to what is above, and what is above corresponds to what is below. It is within a membrane, through which it filters what is drinkable and takes in its nourishment. All of them have a head, but apart from the part that receives nourishment, the other parts of the body are nameless. [section 1] All the soft-shelled creatures are also capable of walking, and that is why they have many feet. The largest kinds of them are four: the ones called spiny lobsters, lobsters, shrimp, and crabs; and of each of these there are several species differing not only in shape but also greatly in size, for some of them are large and others altogether small.

31| [section 2] Now the crab-like and the lobster-like kinds are alike in that both have claws. They do not have these for the sake of walking, but for grasping and holding, in place of hands. That is also why they bend these in the opposite way from their feet: they bend and curl their feet toward the concave side, but their claws toward the convex side, for in this way the claws are useful for taking hold of food and bringing it to the mouth. [section 3] They differ in that spiny lobsters have a tail, while crabs do not have a tail. For the tail is useful to the former because they are swimmers—they swim by pushing off with it as if with oars—but to crabs it is of no use, because their way of life keeps close to the ground and they live in holes. [section 4] And those of them that live in the open sea have, for this reason, feet that are much more sluggish for walking—for example spider-crabs and the crabs called Heracleotic—because they make use of little motion, and their safety comes instead from being shell-like; that is why spider-crabs have thin legs, and the Heracleotic crabs have small legs.

32| [section 5] But the altogether small crabs, which are caught among the tiny fish, have their last pair of feet flat, so that they may be useful to them for swimming, their feet being like oar-blades, as if they were fins. Shrimp differ from the crab-like kinds in having a tail, and from the lobster-like kinds in not having claws; they do not have claws because they have more feet—for the growth that would have gone into the claws has been spent there instead—and they have more feet because they are more given to swimming than to walking. [section 6] The parts on their underside and around the head that serve to take in water and let it out are gill-like. Female spiny lobsters have their lower parts broader than the males do, and female crabs have the parts under the flap hairier than the males, because they extrude their eggs onto these parts rather than at a distance, as fish and the other creatures that bear young do; for being broader, these parts provide more room, a greater space, for the eggs. [section 7] So all spiny lobsters and crabs have their right claw larger and stronger, for all animals are by nature disposed to act more with their right side, and nature always assigns each organ to those able to use it, either exclusively or more than the other—

33| for example tusks, teeth, horns, spurs, and all such parts as serve for defense and strength. [section 8] Lobsters alone have the larger of their two claws on whichever side it happens to be, in both females and males. The cause of their having claws at all is that they belong to the genus that has claws; but they have this irregularly because they are defective in this respect and do not use their claws for what they are naturally suited for, but for the sake of walking. [section 9] As for each of the parts individually—their position, their differences from one another, and, among other things, how the males differ from the females—let this be studied from the Dissections and from the Researches on Animals. [section 1] As for the cephalopods, their internal parts have been discussed earlier, as with the other animals. Externally they have the trunk of the body, which is undifferentiated, and, belonging to this, feet in front around the head, inside the eyes, around the mouth and the teeth. Now the other animals that have feet have some in front and some behind, or else at the side, as with the many-footed bloodless animals; but this kind is peculiar among these, for they have all their feet on what is called the front.

34| [section 2] The cause of this is that their hind part has been drawn together toward the front, as with the spiral-shaped testaceans. For in general the testaceans stand, in one respect, like the crustaceans, and in another, like the cephalopods: insofar as the earthy part is outside and the fleshy part inside, they are like the crustaceans, but in the way the shape of the body is put together, they are like the cephalopods—in a way all of them, but especially, among the spiral-shaped kinds, those that have the coil. For in both, nature follows this same arrangement, as one might conceive it laid out along a straight line, just as happens in the case of four-footed animals and human beings: first, at the upper end of the straight line, the mouth, at point A; then B the gullet, and Γ the stomach; and from the intestine down to the outlet for the residue, where Δ is. [section 3] This, then, is how it is arranged in the blooded animals, and around this are situated the head and what is called the thorax. The remaining parts nature added for the sake of these organs and for the sake of motion—for example the front limbs and the hind ones. In the crustaceans and the insects too, the straight-line arrangement of the internal organs tends to follow the same pattern, but in respect to the external moving parts that serve them, they differ from the blooded animals.

35| [section 4] 4 The soft-bodied animals (the cephalopods) and the spiral-shelled testaceans have their parts arranged in the same way as each other, but in the reverse way from the crustaceans and the rest. For the end is bent back toward the beginning, as if one bent the straight line on which E lies and brought D up to A. For with the internal organs lying in this way, the cephalopods have wrapped around them the sac — which is called, only in the case of the octopuses, the head; and in the testaceans the corresponding structure is the spiral shell. [section 5] 5 There is no other difference except that in the one case nature has put a soft covering around the fleshy part, and in the other a hard one, so that the animal may be preserved despite its difficulty in moving; and for this reason the residue passes out near the mouth in both the cephalopods and the spiral-shelled animals, except that in the cephalopods it comes out from below, and in the spiral-shelled ones from the side. [section 6] 6 It is for this cause, then, that the feet of the cephalopods are arranged in this way, and in the opposite manner from those of other animals. Cuttlefish and squid have them unlike the octopuses, because they only swim and do not also walk. For they have six small arms above the mouth-parts, and of these the two outermost are larger, while of the remaining eight the two below are the largest of all. For just as in four-footed animals the hind limbs are the stronger, so in these creatures the lower arms are the largest; for it is these that bear and move the load most of all, and the two outermost are larger than the middle ones because they assist these lower ones. The octopus, by contrast, has the four middle arms the largest.

36| [section 7] 7 All these animals, then, have eight of these feet, but in the cuttlefish and squid they are short, while in the octopus-like animals they are long. For the former have a large body-sac and the latter a small one, so that nature took away from the body in the one case and added to the length of the feet, while in the other case she took from the feet and used it to increase the body. This is why in the octopuses the feet are useful not only for swimming but also for walking, while in the cuttlefish and squid they are useless for this — for they are small, while the sac is large. [section 8] 8 Since they have short feet, useless for taking hold of things and for not being torn away from the rocks when there is surf and storm, and useless for drawing distant things toward them, for these reasons they have two long tentacles, with which they anchor themselves and ride at their moorings the way a ship does in a storm, and with which they hunt and draw toward themselves things at a distance; and both the cuttlefish and the squid have these. The octopuses do not have such tentacles, because their feet serve them for these purposes. [section 9] 9 Those creatures which have suckers attached to their feet, arranged along the tentacle-arms, possess a power and a construction of the sort found in the little woven devices which the ancient physicians used to insert their fingers into; for these too are woven out of fibers, and with them the animals grip

37| the flesh and anything that yields to them. For being slack they close loosely around a thing; but when the animal draws them tight, the sucker presses and holds fast on every part of what it touches within it. Since, then, there is nothing else with which they can draw things toward them — apart from what they take with their feet on the one hand and with their tentacles on the other — they have these suckers for defense and for other kinds of assistance, in place of hands. [section 10] 10 Now the rest have two rows of suckers, but a certain kind of octopus has only one row. The cause of this is the length and slenderness of their bodily nature; for a narrow arm must necessarily have only one row. They do not have this arrangement, then, because it is best, but because it is necessary given the particular character of their substance. [section 11] 11 All of these creatures have a small fin running round the sac. In most of them this is joined together and continuous, as also in the large squid; but the smaller ones, called squid in the narrower sense, have this fin broader and not narrow, as the cuttlefish and octopuses do, and it begins from the middle and does not run all the way round in a circle. They have this so that they may swim and so as to steer themselves, just as flying creatures have the rump feather and fish have the tail-fin. [section 12] 12 This part is smallest and least noticeable in the octopuses, because they have a small sac and steer adequately with their feet. We have now spoken about the insects, the crustaceans, the testaceans, and the cephalopods, both about their internal parts and about their external ones.

38| 10 We must again take up from the beginning the study of the blooded, live-bearing animals, starting from the parts that remain and have not yet been discussed; and once these have been distinguished we shall speak in the same way about the blooded, egg-laying animals. Now the parts around the head of animals have already been discussed, and those around the so-called neck and throat. All blooded animals have a head;

39| but in some of the bloodless animals this part is not clearly marked off, as in the crabs. All live-bearing animals, then, have a neck, but of the egg-laying animals some have one and some do not: those that have lungs also have a neck, while those that do not breathe from outside do not have this part. The head exists mainly for the sake of the brain; for blooded animals must necessarily have this part, and it lies in the position opposite to the heart, for the reasons stated earlier. Nature has also placed in the head some of the sense organs, because the blend of blood there is well-proportioned and suited both to the warmth of the brain and to the stillness and precision required by the senses. Further, she set beneath it as a third part the structure that provides the entrance for nourishment; for it was there that this could be placed most proportionately. For the mouth-cavity could not lie above the heart and the ruling principle, nor, given that it lies below as it now does, could its entrance be placed still lower than the heart; for then the length of the body would be great, and the entrance would be too far from the principle that moves and concocts the food. The head, then, exists for the sake of these things, and the neck for the sake of the windpipe; for it is a protection, and preserves this and the gullet by enclosing them all around. In most animals the neck is flexible and has vertebrae, but wolves and lions have a neck made of a single bone; for nature looked to making it useful for strength rather than for other kinds of assistance. Next after the neck and the head come, in animals, the forelimbs and the chest. Man, instead of forelegs and forefeet, has arms and what are called hands. For man alone stands upright

40| of the animals, because its nature and its substance are divine; and the work of what is most divine is thinking and exercising practical wisdom. This is not easy when a great deal of body lies weighing on top; for bulk makes thought and the common perception hard to move. Hence, as the bulk and the bodily mass become greater, the bodies are necessarily drawn down toward the earth, so that for the sake of stability nature has furnished four-footed animals with front feet instead of arms and hands. For all animals capable of walking must have two hind feet; and such animals became four-footed because the soul was not able to carry the bulk. For all the other animals are dwarfish in comparison with man: a thing is dwarfish when its upper part is large but the part that carries the bulk and walks on the ground is small. The upper part is what is called the trunk, from the head to the outlet for residue. In human beings this is proportionate to the lower part, and becomes much smaller as they reach maturity; but in the young it is the opposite: the upper parts are large and the lower part small. That is why they crawl and are not able to walk. And at the very first stage they cannot even crawl, but remain motionless, for all infants are dwarfs. As human beings advance, the lower parts grow; but in four-footed animals it is the opposite: the lower parts are largest at first, and as they advance the upper parts grow — this being the mass that runs from the seat to the head. That is why foals are little if at all shorter in height than grown horses, and while young they can touch their head with a hind leg, but when older they cannot. This, then, is how it is with the solid-hoofed and cloven-hoofed animals; the many-toed and hornless animals are dwarfish too, but less so than these.

41| That is why such animals make their growth in the upper parts proportionate to the deficiency in the lower parts. And the class of birds, and the class of fish, and every blooded animal, as has been said, is dwarfish. That is also why all animals are less intelligent than human beings. Indeed, even among human beings — for example children compared to grown men, and among grown men themselves those who are dwarfish in nature — even if they possess some other capacity in excess, they are deficient in the possession of intellect. The cause, as has been said before, is that the principle of the soul is very hard to move and bodily in them. Further, as the heat that lifts the body up becomes less and the earthy element becomes more, the bodies of the animals become smaller and many-footed, and in the end become footless and stretched out flat along the ground. And going a little further still in this progression, they even have their starting principle below, and the part corresponding to the head is in the end motionless and without perception, and the creature becomes a plant, having its upper parts below and its lower parts above; for the roots have, for plants, the capacity of a mouth and a head, while the seed is the opposite — for it forms above, at the tips of the shoots. The cause, then, why some animals are two-footed, others many-footed, and others footless, and the cause why some things have become plants and others animals, has been stated, and also why man alone among the animals stands upright. Since he is upright in nature, he has no need of front legs at all, and in their place nature has given him arms and hands instead. Anaxagoras, then, says that man is the most intelligent of the animals because he has hands; but it is reasonable to suppose that he has hands because he is the most intelligent. For hands are an instrument, and nature, like a practically wise person, always distributes each

42| thing to the one able to use it. For it is fitting to give flutes to one who is already a flute-player, rather than to fit flute-playing onto one who already has flutes; for she has added the lesser thing to the greater and more authoritative thing, not the more valuable and greater thing to the lesser. If, then, this is the better way, and nature always does, out of the possibilities available, what is best, it is not on account of the hands that man is the most intelligent, but on account of being the most intelligent of the animals that he has hands. For the most intelligent being would make good use of the greatest number of instruments, and the hand seems to be not one instrument but many; for it is, as it were, an instrument in place of instruments. To the being capable of receiving the greatest number of crafts, then, nature has given the hand, the instrument useful for the greatest number of purposes. But those who say that man is not put together well, but worst of all the animals — for they say he is unshod and naked and without a weapon for defense — do not speak correctly. For the other animals have a single means of assistance, and it is not possible for them to exchange this for another; rather, they are compelled to sleep, so to speak, still shod, and to do everything so, and never to lay aside their protection for the body, nor to exchange whatever weapon they happen to have; whereas the human being has many means of assistance, and it is always possible to exchange these, and further to have whatever weapon he wishes and wherever he wishes. For the hand becomes claw and hoof and horn and spear and sword and any other weapon or instrument whatsoever; for all these it will be, because it is able to take and hold them all. And to this end the form [and] the nature of the hand has been contrived accordingly. For it is divisible and many-cleft; and it belongs to what is divisible to be also composite, whereas the reverse of this

43| does not hold. And it is possible to use it with one finger, or with two, or in many ways. And the joints of the fingers are well suited for grasping and pressing. And there is one finger set at an angle to the side, and this one is short and thick, not long; for just as, if there were no hand at all, there would be no grasping, so likewise there would be none if this finger did not stand to the side. For this one presses from below upward, which the others do from above downward; and this must happen if the grip, like a strong bond, is to bind firmly, so that being one it may be equal in force to the many. And it is short both for the sake of strength and because a long one would be of no use. And the outermost finger is rightly small, and the middle one long, like an oar amidships; for what is grasped must most of all be enclosed all round at the middle for the work to be done. And this is why, though small, it is called great, because the other fingers are, so to speak, useless without it. And the arrangement of the nails, too, is well contrived: the other animals have them for use as well, but for human beings they are coverings, being a protection for the extremities. And the joints of the arms bend, for bringing food to the mouth and for other uses, in the opposite way from the four-footed animals. For those animals must bend their front limbs inward, since they use them as feet, so that they may be useful for walking, since indeed even among these, in the many-toed kinds, the front legs are useful not only for walking but also in place of hands, as in fact they are seen to be used; for they both grasp and defend themselves with the front limbs. But the solid-hoofed animals defend themselves with the hind limbs; for their front legs bear no analogy to elbows and hands. Some of the many-toed animals also have, for this reason, five toes on their front feet, but the

44| Some are four-toed behind, for instance lions and wolves, and also dogs and leopards; for the fifth toe, as in the hand, becomes in effect the large fifth. But the small many-toed animals have five toes even on the hind feet, because they are climbers, so that with more claws to grip they can more easily climb up to what is higher and above their heads. Between the elbows in human beings, and between the front legs in other animals, is what is called the chest. In human beings it reasonably has breadth, since the elbows, being set to the side, do not prevent this region from being broad; but in four-footed animals, because of the forward extension of the front limbs in walking and changing place, this part is narrow. And for this reason four-footed animals do not have breasts in this region; but in human beings, because of the roominess there and because the region around the heart needs to be covered, since the place is fleshy the breasts have accordingly become differentiated, being fleshy in the males for the reason stated, while in the females nature has additionally put this fleshy place to use for another function as well, which we say nature often does: for it stores up nourishment there for the offspring. There are two breasts because there are two sides, the left and the right. And they are rather firm, but distinct, because the ribs also join together at this place, though their nature is not laborious. In other animals it is impossible for the breasts to be, awkwardly, on the chest between the legs (for they would then get in the way of walking), and they have them in many different arrangements. For the animals that bear few young, are single-hoofed, and horn-bearing

45| have their breasts on the thighs, and these are two; but the animals that bear many young, or that are many-toed, have theirs either arranged along the belly, to the side and numerous, as in the pig and the dog, or only two, near the middle of the belly, as in the lion. The cause of this is not that the lion bears few young — since it sometimes bears more than two — but that it is not abundant in milk; for it uses up the nourishment it takes in on its own body, and it takes in little, because it is carnivorous. The elephant has only two, and these under the armpits of the front legs. The cause of its having two is that it bears a single offspring; the cause of their not being on the thighs is that it is many-toed (for no many-toed animal has breasts on the thighs); and the cause of their being up near the armpits is that these are the first breasts among those animals that have many breasts, and these yield the most milk. A sign of this is what happens with pigs: to the first-born of the piglets they offer the first breasts; so whatever animal's first-born is a single one must have the first breasts, and the first are those under the armpits. The elephant, then, for this reason has two breasts and in this place, while the many-bearing animals have theirs about the belly.

46| The cause of this is that those that are going to nurse more offspring need more breasts; since, then, it is not possible to have more than two arranged in breadth, because there are only two sides, left and right, they must have them arranged in length. Now the region between the front legs and the hind legs has length only. Animals that are not many-toed but bear few young, or are horn-bearing, have their breasts on the thighs, for instance the horse, the ass, the camel (for these bear a single offspring, and some are single-hoofed while the camel is cloven-hoofed), and further the deer and the ox and the goat and all the other animals of this kind.

47| The cause is that in these animals growth is toward the upper part of the body. So wherever there is a gathering and abundance of residue and blood — and this place is the lower part, around the outlets — there nature has made the breasts; for from wherever the movement of nourishment occurs, from there it is also possible for the young to take it. Now the human being, both female and male, has breasts, but among the other animals some of the males do not have them, for instance among horses some do not have them and some do, namely those that resemble their mother. So much, then, for the breasts. After the chest comes the region around the belly, not enclosed by the ribs, for the reason stated before, so that the ribs may not obstruct either the swelling of the food, which necessarily occurs as it is heated, or the womb during pregnancy. The end of what is called the trunk is the parts concerned with the passage of the residue, both the dry and the moist. Nature makes additional use of the same part both for the passage of the moist residue and for copulation, alike in the females and in the males, in nearly all blood-bearing animals except a few, and in all the live-bearing ones.

48| The cause is that the seed is something moist, and a residue; let this be assumed for now, and it will be demonstrated later concerning it. In the same way too, in the females, both the menstrual fluid and the passage by which they emit the seed follow the same pattern; this too will be determined later, but for now let it only be assumed that the menstrual fluid, like the seed, is a residue in females. The menstrual fluid and the seed are moist in their nature, so it stands to reason that the discharge of the same and of similar things should be into these same parts. How matters stand internally, and in what way the organs concerned with seed and those concerned with pregnancy differ, is evident from the History of Animals and from dissections, and will be discussed later in the works on generation. That the shapes of these parts, too, are necessarily suited to their function is not unclear. [section 32] The organ of the males has differences corresponding to the differences of body. For not all animals are alike sinewy in nature. Further, this alone among the parts undergoes growth and diminution without being a diseased change; for one of these states is useful for coupling, the other for the use of the rest of the body — since if it were always in the same state it would get in the way.

49| [section 33] This part is composed, in its nature, of such materials that both these outcomes can occur: for part of it is sinewy and part cartilaginous, and for this reason it is able both to contract and to extend, and it is capable of receiving breath. Now the females of the four-footed animals are all backward-urinating, because that position is useful to them for copulation in this way; but of the males few are backward-urinating, for instance the lynx, the lion, the camel, the hare; and no single-hoofed animal is backward-urinating. [section 34] The hind parts and what concerns the legs are peculiar to human beings as against the four-footed animals. Almost all animals have a tail, not only the live-bearing ones but the egg-laying ones too; for even if this part has no size in them, still for the sake of a mark they have some sort of projection. [section 35] The human being is tailless, but has hips, which none of the four-footed animals has. Further, as regards the legs, the human being has fleshy thighs and shins, while all the other animals have fleshless ones — not only the live-bearing animals but, generally, all animals that have legs; for they have sinewy and bony and spiny legs.

50| [section 36] There is, one might say, a single cause of all these things: that man alone among animals stands upright. So that he might easily carry the upper parts, which are light, nature took the bodily bulk away from the upper parts and added the weight to the lower ones; that is why it made the hips, thighs, and calves fleshy. [section 37] At the same time nature made the nature of the hips useful also for resting. For four-footed animals find standing untiring, and do not grow weary doing this continuously (since, with four supports underneath, it is as if they remain lying down the whole time), but for men it is not easy to remain standing upright continuously; rather the body needs rest and a seat. [section 38] Man, then, has hips and fleshy legs for the reason stated, and for this same reason is tailless (for the nourishment that would go there is used up on these parts instead, and because he has hips, the necessary use of a tail has been taken away). But the four-footed animals and the other animals are the opposite way: since they are dwarfed toward the top, all the weight and bodily bulk lies upon the upper part, taken away from the lower parts; that is why they have hipless legs, and hard ones.

51| [section 39] So that the part serving the discharge of residue might be guarded and covered, nature gave them the so-called tail, taking away for it from the nourishment that goes to the legs. But the ape, because its form is ambiguous and belongs neither wholly to one type nor wholly to the other, but to both, for this reason has neither tail nor hips: no tail, in that it is two-footed, and no hips, in that it is four-footed. [section 40] Of the so-called tails there are several differentiae, and nature makes further use of them too in these animals, not only for guarding and covering the seat, but also for benefit and use to those that have them. Feet, again, differ among four-footed animals: some of them are single-hoofed, some cloven-hoofed, some many-toed. They are single-hoofed in those which, because of their size and because they have a great deal of earthy matter, received such a part as a secreted growth into the nature of a claw, in place of horns and teeth; and because of its bulk, the hoof is a single claw in place of several claws. [section 41] And for this reason such animals generally do not have an astragalus, because the bending of the hind leg would be harder to move if an astragalus were present in it; for joints with a single angle open and close faster than those with several, and the astragalus, being a peg-like bone, is set in between the two bones like a foreign limb, adding weight but making the stance more secure.

52| [section 42] For this same reason, those animals that do have an astragalus have it not in the forelegs but in the hind legs, because the legs that lead the way must be light and easy to bend, while security and firmness belong in the hind legs. Further, for the sake of defense, this makes the blow heavier; for such animals use their hind limbs for defense, kicking out at whatever troubles them. [section 43] Cloven-hoofed animals have an astragalus (since their hind legs are the lighter part), and because they have an astragalus they are also not single-hoofed, the astragalus being, as it were, the bony part left over from the foot, remaining at the bend. Many-toed animals do not have an astragalus; for if they had one, they would not be many-toed, but the foot would be split in breadth only as far as the astragalus extends. That is why, of the animals that do have it, most are cloven-hoofed. [section 44] Man has the largest feet of the animals in proportion to his size, and reasonably so; for he alone stands upright, so that feet which, being only two, are going to bear the entire weight of the body must have both length and breadth. And indeed the size of the toes stands in an opposite relation on the feet and on the hands, proportionately speaking; for the function of the hands is to take hold and

53| to grip, so that they must have long fingers (for the hand grasps round an object with the part that bends), whereas the function of the feet is to stand securely, so that one must reckon that this is the part of the foot that matters: the undivided part apart from the toes. [section 45] Yet it is better for the extremity to be divided than undivided; for otherwise the whole would suffer together whenever a single part were injured, whereas when it is split into toes this does not happen in the same way. [section 46] Further, being short, the toes are less liable to be harmed; that is why human feet are many-toed but not long-toed. And for the same reason people have the class of nails on the hands as well; for the extremities need covering most of all, because of their weakness. [section 1] Concerning the blooded, viviparous, land-dwelling animals, then, we have spoken about nearly everything. Of the blooded animals that are egg-laying, some are four-footed and some footless. There is only one such genus that is footless, that of the snakes; the cause of their footlessness has been stated in the discussions determined concerning the progression of animals. The rest have a form similar to that of the four-footed, viviparous animals. [section 2] These animals have a head, and the parts in it, for the same causes as the other blooded animals do, and a tongue in the mouth, except for the river crocodile; this one would not seem to have one, but only the place for one.

54| [section 3] The cause is that in a way it is at once a land animal and a water animal: because it is a land animal it has a place for a tongue, but because it is a water animal it is tongueless. For fish, as has been said before, in some cases do not appear to have one, unless one tilts the head sharply back, and in other cases have one that is undifferentiated. [section 4] The cause is that these animals had little need of a tongue, because they cannot chew or taste in advance; rather, for all of them the perception and pleasure of their food occurs in the swallowing. For the tongue produces the perception of flavors, whereas the pleasure of foods occurs in their passage down; for as they are swallowed, they perceive what is fatty and hot and other such qualities. [section 5] The viviparous animals too have this perception, and for most relishes and foods the enjoyment occurs, in the swallowing, through the stretching of the gullet. That is why the same creatures are not without self-control in the same way about drinks and flavors as about relishes and food; rather, the other animals possess the perception by way of taste as well, while these have, so to speak, only the other kind of perception.

55| [section 6] Among the four-footed, egg-laying animals, lizards, like snakes, have a forked tongue, altogether hair-like at the tip, as has been said before. Seals too have a forked tongue; that is why all these animals are also gluttonous. The four-footed egg-laying animals also have saw-edged teeth, like fish. All of them have sense-organs like those of the other animals, namely nostrils for smell, eyes for sight, and ears for hearing, except that these are not raised up, just as with birds, but consist only of the passage. [section 7] The cause of both facts is the hardness of the skin; for birds are feathered, while these are all scaly, and the scale is similar in kind to a fish-scale, but by nature harder. This is shown in the case of tortoises, of large snakes, and of river crocodiles; for these grow stronger than bone, being of such a nature. These animals do not have an upper eyelid, just as birds do not either, but close the eye with the lower one, for the reason stated in their case. [section 8] Now some of the birds also blink

56| by a membrane from the corners of the eyes, and these animals do not blink; for they are harder-eyed than birds. The cause is that for birds keen sight is more useful for their way of life, since they are winged, but for these animals it is less useful; for all such animals are burrow-dwellers. Since the head is divided into two parts, the upper part and the lower jaw, man and the four-footed animals that bear live young move their jaws both up and down and also sideways, while fish, birds, and the four-footed animals that lay eggs move them only up and down. [section 9] 9 The cause is that this up-and-down motion is useful for biting and dividing, while the sideways motion serves for grinding smooth. Now for those that have molars the sideways motion is useful, but for those that do not have molars it is of no use at all, and so it has been taken away from all such animals; for nature does nothing superfluous. [section 10] 10 Now all the other animals move the lower jaw, but the river crocodile alone moves the upper. The cause of this is that its feet are useless for grasping and holding fast, since they are altogether small. For these purposes, then, nature has made its mouth useful to it in place of feet.

57| [section 11] 11 For holding fast or grasping, whichever side the blow is stronger from is the more useful side to move; and the blow is always stronger from above than from below. Since, then, both uses are performed through the mouth, both grasping and biting, and holding fast is more necessary for a creature that has neither hands nor well-formed feet, it is more useful for such creatures to move the upper jaw than the lower. [section 12] For the same reason crabs too move the upper 12 part of the claw, and not the lower; for they have their claws in place of hands, so that the claw needs to be useful for grasping, not for dividing. Dividing and biting are the work of teeth. Now for crabs, and for the other animals for which it is possible to take food at leisure because the use of the mouth is not carried on in a liquid medium, the functions are divided: they grasp with hands and feet, but divide and bite with the mouth. [section 13] But for crocodiles nature has made the mouth 13 useful for both purposes, the jaws being moved in this way. And all such animals have a neck because they have a lung; for they take in breath through the windpipe, which has length.

58| [section 1]

59| 13 The parts of birds, then, are in this condition. The class of fish is stunted still further in its external parts. For they have neither legs nor hands nor wings (the cause of this has been stated before), but the whole trunk is continuous from the head all the way to the tail. This tail is not alike in all of them; some have one much the same, but among the flat fish some have a tail that is spiny and long, since the growth from that region goes into breadth, as with electric rays and stingrays and any other cartilaginous fish of that kind. In these, then, the tail-part is spiny and long, but in some it is fleshy and short, for the same cause as with the electric rays; for it makes no difference whether it is short and fleshier, or long and less fleshy. In the anglerfish the opposite has happened: because their forward breadth is not fleshy, whatever flesh has been withheld from there nature has placed toward the rear, in the tail as well. Fish do not have detached limbs because their nature, by the account of their substance, is a swimming one, since nature makes nothing superfluous or in vain. But since they are blooded in their substance, they have fins because they are swimmers, and they do not have feet because they do not go on land; for the addition of feet is useful for movement over flat ground. And it is not possible to have four fins and feet at the same time, nor any other such limb besides; for they are blooded. Tadpoles, however, though they have gills, have feet; for they have no fins, but a tail that is loose-textured and broad. Among fish, those that are not flat, such as the ray and the stingray, have four fins, two on

60| the dorsal side and two on the ventral side. None has more than these; for they would then have been bloodless. Of these, nearly all have the dorsal ones, but some of the long, thick-bodied ones do not have the ventral ones, such as the eel and the conger eel and a certain kind of grey mullet found in the lake at Siphae. Those that are of longer growth and more snake-like, such as the moray eel, have no fin at all, but move by their bendings, using the water just as snakes use the land; for snakes swim in the very way that they crawl on land. The cause of the snake-like fish not having fins is the same as the cause of snakes being footless. The cause has been stated in the work on the progression and movement of animals. For otherwise they would move badly, moving by four points. For if they had their fins close together, they would move only with difficulty, and if far apart, likewise, because of the great distance between them. And if they had had more points of motion, they would have been bloodless. The same cause holds also for the fish that have only two fins; for they are snake-like and rather elongated, and use bending in place of the other two fins.

61| This is also why they crawl on dry land and can live a long time out of water, and some do not die at once, while those that are akin in nature to land-going creatures thrash about less. Of the fins themselves, those fish that have only two fins have them on the dorsal side, except where breadth prevents it. Those that have them near the head have them there because they lack length in the region by which they would otherwise move; for the body of such fish is elongated toward the tail. Rays and the like swim by means of their outermost breadth in place of fins. But those that have less breadth have fins, such as the electric ray and the anglerfish, the

62| ones on the dorsal side set lower down, because of the breadth of the upper part, and the ones on the ventral side near the head (for the breadth does not prevent motion there); but instead of being on top, these are smaller than the dorsal ones. The electric ray has its two other fins near the tail; and instead of two more fins it uses its breadth, employing each semicircular lobe as a fin. The parts in the head and the sense-organs have been discussed earlier. The class of fish has, as its own peculiar feature compared with the other blooded animals, the nature of the gills; the cause of this has been stated in the work on respiration. And among the fish that have gills, some have coverings over their gills, while all the cartilaginous fish (for they are cartilage-spined) have them uncovered. The cause is that the covered ones are spiny, and the covering itself is spiny, while all the cartilaginous fish have cartilage in place of spine. Moreover, the movements of the cartilaginous ones are sluggish because they are neither spiny nor sinewy, while the movements of the spiny ones are quick; and the movement of the covering must be quick, since the nature of the gills serves, as it were, for exhalation. For this reason, in the cartilaginous fish the contraction occurs in the gill-passages themselves, and there is no need of a covering, so that it may happen quickly.

63| Now some of them have many gills and some few, and some have double gills and some single; but the last gill is single in most of them. The precise details about these must be studied from the dissections and in the Researches on Animals. The cause of the multiplicity or paucity of gills is the multiplicity or paucity of the heat in the heart; for those that have more heat need a quicker and stronger motion. More numerous and double gills have this nature more than single and fewer ones do. This is also why some of them can live out of water for a long time, being of those

64| Those with fewer and weaker gills, such as the eel and the snake-like fish, need little cooling. There are also differences in the mouth. Some fish have the mouth straight ahead, facing forward, others have it on the underside, as dolphins and the cartilaginous fish do; hence they take their food by turning over onto their backs. Nature appears to have done this not only for the safety of the other animals (for while the fish is delayed in turning over, the others escape, since all such fish are flesh-eaters), but also so that these fish should not indulge their gluttony for food; for if they took it easily, they would quickly destroy themselves by overfilling. Besides this, they cannot have a widely-cleft mouth. Further, among fish that have the mouth on top, some have it wide-slit and some tapering to a point: those that are carnivorous have it wide-slit, like the saw-toothed fish, because for such fish their strength lies in the mouth, while those that are not carnivorous have it tapering. As for the skin, some fish have scaled skin (the scale stands off from the body owing to the body's brightness and thinness), like the angel-shark and the ray and such fish; very few are smooth-skinned. The cartilaginous fish are without scales but are rough, because they have cartilage in place of spine; for nature has spent the earthy matter that would otherwise have gone there upon the skin instead. No fish has testicles, either external or internal, nor does any other footless animal, and so neither do snakes. They have the same passage for residue and for the parts concerned with generation, just as all the other egg-laying animals do, including the four-footed ones, because they have no bladder and produce no liquid residue. The class of fish, then, has these differences from the other animals,

65| and dolphins and whales and all such cetaceans have no gills, but have a blowhole because they have a lung; for they take in seawater through the mouth and let it out through the blowhole. They must take in the water because they take their food in the water, and having taken it in they must let it out again. Gills, then, are useful to animals that do not breathe; the reason has been stated in the work on respiration; for it is impossible for the same animal both to breathe and to have gills. But these animals have the blowhole for letting out the water. It is situated in front of the brain, since, placed elsewhere, it would have cut the brain off from the spinal cord. The reason these animals have a lung and breathe is that large animals need more heat in order to move; hence a lung, full of blood-heat, is present in them. These animals are, in a way, both land-animals and water-animals: they take in air as land-animals do, but they are footless and get their food from the water, like water-animals. Seals too, and bats, because they belong ambiguously to both classes — the seals to the water-animals and the land-animals, the bats to the winged animals and the land-animals — for this reason share in both and in neither. For seals, as water-animals, have feet, yet as land-animals they have flippers (for their hind feet are entirely fish-like, and besides, all their teeth are saw-edged and sharp); and bats have feet in the manner of winged creatures, but not in the manner of four-footed ones, and they have neither a tail nor a rump — they have neither a tail nor a rump — no tail, because they are winged; no rump, because they are land-animals. This happens to them of necessity; for they have wings of skin, and nothing has a rump unless it has split feathers; for it is out of that kind of feather that the

66| rump forms. As for a tail, it would actually have been an obstacle if present amid their wings. In the same way too the Libyan ostrich has some features of a bird and some of a four-footed animal. As not being a four-footed animal, it has feathers; but as not being a bird, it does not fly up into the air, and its feathers are not useful for flight but are hair-like. Further, as being a four-footed animal, it has eyelashes on the upper lid and is bare about the head and the upper part of the neck, so that its eyelashes are rather hair-like; but as being a bird, it is feathered on the lower parts, and it is two-footed as a bird is, but cloven-hoofed as a four-footed animal is, for it has not toes but hooves. The reason for this is that it has the size not of a bird but of a four-footed animal; for the size of birds, generally speaking, must necessarily be small, since it is not easy for a great bulk of body to move while lifted in the air. Concerning the parts, then — for what cause each one is present in animals — we have spoken of all the animals one by one. Now that these matters have been determined, it remains next to go through the subject of their generation.

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