The Politics of Aristotle

by Aristotle

  [675a1] Fishes are provided with teeth, which in almost all of them are of the saw-toothed kind. For there is but one small group in which it is otherwise. Of these the fish called Scarus is an example. And this is probably the reason why this fish [5] apparently ruminates, though no other fishes do so. For those horned animals that are not ambidentate also ruminate.

  In fishes the teeth are all sharp; so that these animals can divide their food, though imperfectly. For it is impossible for a fish to linger or spend time in the act of mastication, and therefore they have no teeth that are flat or suitable for grinding; for such teeth would be to no purpose. The oesophagus again in some fishes is [10] entirely wanting, and in the rest is short. In order, however to facilitate the concoction of the food, some of them, as the mullet, have a fleshy stomach resembling that of a bird; while most of them have numerous appendages close against the stomach, to serve as a sort of antechamber in which the food may be stored up and undergo putrefaction and concoction. There is a contrast between [15] fishes and birds in the position of these appendages. For in fishes they are placed high up, close to the stomach; while in birds, if present at all, they are lower down, near the end of the gut. Some of the Vivipara also have appendages connected with the lower part of the gut which serve the same purpose as that stated above.

  The whole tribe of fishes is of gluttonous appetite, owing to the arrangements [20] for the reduction of their food being very imperfect, and much of it consequently passing through them without undergoing concoction; and, of all, those are the most gluttonous that have a straight intestine. For as the passage of food in such cases is rapid, and the enjoyment derived from it in consequence but brief, it follows of necessity that the return of appetite is also speedy.

  [25] It has already been mentioned that in ambidentates the stomach is of small size. It may be classed pretty nearly always under one or other of two headings, namely as resembling the stomach of the dog, or as resembling the stomach of the pig. In the pig the stomach is larger than in the dog, and presents certain folds of moderate size, the purpose of which is to lengthen out the period of concoction; while the stomach of the dog is of small size, not much larger in calibre than the gut, [30] and smooth on the internal surface.

  For in all animals after the stomach comes the gut. This, like the stomach, presents numerous modifications. For in some animals it is uniform, when uncoiled, and alike throughout, while in others it differs in different portions. Thus in some cases it is wider in the neighbourhood of the stomach, and narrower towards the [35] other end; and this explains by the way why dogs have to strain so much in discharging their excrement. But in most animals it is the upper portion that is the [675b1] narrower and the lower that is of greater width.

  Of greater length than in other animals, and much convoluted, are the intestines of those that have horns. These intestines, moreover, as also the stomach, are of ampler volume, in accordance with the larger size of the body. For animals with horns are, as a rule, large, because of the thorough elaboration which their food [5] undergoes. The gut, except in those animals where it is straight, invariably widens out as it gets farther from the stomach; then they have what is called the colon, and the blind and swollen part of the gut. After this it again becomes narrower and convoluted. Then succeeds a straight portion which runs right on to the vent. This [10] vent is known as the anus, and is in some animals surrounded by fat, in others not so. All these parts have been so contrived by nature as to harmonize with the various operations that relate to the food and its residue. For, as the residual food gets farther on and lower down, the space to contain it enlarges, allowing it to remain stationary and undergo conversion. Thus is it in those animals which, owing either [15] to their large size, or to the heat of the parts concerned, require more nutriment, and consume more fodder than the rest.

  After this, just as a narrower gut succeeds to the upper stomach, so also does the residual food, when its juice is thoroughly exhausted, pass from the colon and the ample space of the lower stomach into a narrower channel and into the spiral [20] coil, in order that nature can regulate her expenditure and prevent the excremental residue from being discharged all at once.

  In all such animals, however, as have to be comparatively moderate in their alimentation, the lower stomach presents no wide and roomy spaces, though their gut is not straight, but has a number of convolutions. For amplitude of space causes [25] desire for ample food, and straightness of the intestine causes quick return of appetite. And thus it is that all animals whose food receptacles are either simple or spacious are of gluttonous habits, the latter eating enormously at a meal, the former making meals at short intervals.

  Again, since the food in the upper stomach, having just been swallowed, must of necessity be quite fresh, while that which has reached the lower stomach must [30] have had its juices exhausted and resemble dung, it follows of necessity that there must also be some intermediate part, in which the change may be effected, and where the food will be neither perfectly fresh nor yet dung. And thus it is that, in all [35] such animals as we are now considering, there is found what is called the jejunum; which is a part of the small gut which comes next to the stomach. For this jejunum lies between the upper cavity which contains the yet unconcocted food and the lower cavity which holds the useless residual matter. There is a jejunum in all these [676a1] animals, but it is plainly discernible in those of large size when they have abstained from food for a certain time. For then there is a sort of no-man’s land between the two regions, but when they have eaten the time occupied in the transition of food is but brief. In females this jejunum may occupy any part whatsoever of the upper [5] intestine, but in males it comes just before the caecum and the lower stomach.

  15 · What is known as rennet is found in all animals that have a multiple stomach, and in the hare among animals whose stomach is single. In the former the rennet neither occupies the large paunch, nor the honeycomb bag, nor the terminal [10] reed, but is found in the cavity which separates this terminal one from the first, namely in the so-called manyplies. It is the thick character of their milk which causes all these animals to have rennet; whereas in animals with a single stomach the milk is thin, and consequently no rennet is formed. That is why the milk of [15] horned animals coagulates, while that of animals without horns does not. Rennet forms in the hare because it feeds on herbage that has juice like that of the fig; for juice of this kind coagulates the milk in the stomach of the sucklings. Why it is in the manyplies that rennet is formed in animals with multiple stomachs has been stated in the Problems.

  BOOK IV

  1 · The account which has now been given of the viscera, the stomach, and the other several parts holds equally good not only for the oviparous quadrupeds, [25] but also for such footless animals as the Serpents. These two classes of animals are indeed nearly akin, a serpent resembling a lizard which has been lengthened out and deprived of its feet. Fishes, again, resemble these two groups in all their parts, excepting that, while these, being land animals, have a lung, fishes have no lung, but [30] gills in its place. None of these animals, excepting the tortoise, as also no fish, has a bladder. For owing to the bloodlessness of their lung, they drink but sparingly; and such fluid as they have is diverted to the scaly plates, as in birds it is diverted to the feathers, and thus they come to have the same white matter on the surface of their excrement as we see on that of birds. For in animals that have a bladder, its [35] excretion when voided leaves a deposit of earthy brine in the containing vessel. For the sweet and fresh elements, being light, are expended on the flesh.

  [676b1] Among the Serpents, the same peculiarity attaches to vipers, as among fishes attaches to Selachia. For both these and vipers are externally viviparous, but previously produce ova internally.

  The stomach in all these animals is single, just as it is single in all other ambidentates; and their viscera are excessively small, as always happens when there [5] is no bladder. In serpents these viscera are, moreo
ver, differently shaped from those of other animals. For, a serpent’s body being long and narrow, its contents are as it were moulded into a similar form, and thus come to be themselves elongated. [10]

  All animals that have blood possess an omentum, a mesentery, intestines, and, moreover, a diaphragm and a heart; and all, excepting fishes, a lung and a windpipe. The relative positions, moreover, of the windpipe and the oesophagus are precisely similar in them all; and the reason is the same as has already been given. [15]

  2 · Almost all sanguineous animals have a gall-bladder. In some this is attached to the liver, in others separated from that organ and attached to the intestines, being apparently in the latter case no less than in the former an appendage of the lower stomach. It is in fishes that this is most clearly seen. For all fishes have a gall-bladder; and in most of them it is attached to the intestine, being [20] in some, as in the bonito, united with this, like a border, along its whole length. It is similarly placed in most serpents. There are therefore no good grounds for the view entertained by some writers, that the gall exists for the sake of some sensory action. For they say that its use is to affect that part of the soul which is lodged in the neighbourhood of the liver, vexing this part so as to congeal it, and restoring it to [25] cheerfulness when it again flows free. But in some animals there is absolutely no gallbladder at all—in the horse, for instance, the mule, the ass, the deer, and the roe; and in others, as the camel, there is no distinct bladder, but merely small vessels of a biliary character. Again, there is no such organ in the seal, nor, among sea-animals, in the dolphin. Even within the limits of the same genus, some animals [30] appear to have and others to be without it. Such, for instance, is the case with mice; such also with man. For in some individuals there is a distinct gall-bladder attached to the liver, while in others there is no gall-bladder at all. This explains why there is a dispute about the group as a whole. For each observer, according as he has found it present or absent in the individual cases he has examined, has supposed it to be [35] present or absent in the whole genus. The same has occurred in the case of sheep and of goats. For these animals usually have a gall-bladder; but, while in some [677a1] localities it is so enormously big as to appear a monstrosity, as is the case in Naxos, in others it is altogether wanting, as is the case in a certain district belonging to the inhabitants of Chalcis in Euboea. Moreover, the gall-bladder in fishes is separated, [5] as already mentioned, by a considerable interval from the liver. No less mistaken seems to be the opinion of Anaxagoras and his followers, that the gall-bladder is the cause of acute diseases, inasmuch as it becomes over-full, and spurts out its excess on to the lung, the blood-vessels, and the ribs. For, almost invariably, those who suffer from these forms of disease are persons who have no gall-bladder at all, as would be quite evident were they to be dissected. Moreover, there is no kind of [10] correspondence between the amount of bile which is present in these diseases and the amount which is exuded. The most probable opinion is that, as the bile when it is present in any other part of the body is a mere residuum or a collipuescence, so also when it is present in the region of the liver it is a residue and not for the sake of [15] anything; just as is the case with the excretions of the stomach and intestines. For though even the residua are occasionally used by nature for some useful purpose, yet we must not in all cases expect to find such a final cause; for granted the existence of this or that constituent, with such and such properties, many results must ensue as necessary consequences of these properties. All animals, then, whose [20] liver is healthy in composition and supplied with none but sweet blood, are either entirely without a gall-bladder on this organ, or have merely small bile-containing vessels; or are some with and some without such parts. Thus it is that the liver in animals that have no gall-bladder is, as a rule, of good colour and sweet; and that, [25] when there is a gall-bladder, that part of the liver is sweetest which lies immediately underneath it. But, when animals are formed of blood less pure in composition, the bile is the residue left by this. For the very meaning of excrement is that it is the opposite of nutriment, and of bitter that it is the opposite of sweet; and healthy [30] blood is sweet. So that it is evident that the bile is not for the sake of anything, but is a purifying excretion. It was therefore no bad saying of old writers that the absence of a gall-bladder gave long life. In so saying they had in mind deer and animals with solid hoofs. For such have no gall-bladder and live long. But besides these there are other animals that have no gall-bladder, though those old writers had not noticed [35] the fact, such as the camel and the dolphin; and these also are in fact long-lived. Seeing, indeed, that the liver is a necessary and vital part in all animals that have [677b1] blood, it is but reasonable that on its character should depend the length or the shortness of life. Nor less reasonable is it that this organ and none other should have [5] such an excretion as the bile. For the heart, unable as it is to stand any violent affection, would be utterly intolerant of the proximity of such a fluid; and, as to the rest of the viscera, none excepting the liver are necessary parts of an animal. It would be absurd to think that phlegm and the sediment from the stomach are not residues wherever they are found; and clearly the same applies to bile too, and its [10] locality makes no difference.

  3 · So much then of the gall-bladder, and of the reasons why some animals have one, while others have not. We have still to speak of the mesentery and the omentum; for these are associated with the parts already described and contained in [15] the same cavity. The omentum, then, is a membrane containing fat; the fat being suet or lard, according as the fat of the animal generally is of the former or latter description. What kinds of animals are so distinguished has been already set forth in an earlier part of this treatise. This membrane, alike in animals that have a single and in those that have a multiple stomach, grows from the middle of that organ, along a line which is marked on it like a seam. And it covers the rest of the stomach [20] and the greater part of the bowels, and this alike in all sanguineous animals whether they live on land or in water. Now the development of this part into such a form as has been described is the result of necessity. For, whenever dry and moist are mixed together and heated, the surface invariably becomes membranous and skin-like. But the region in which the omentum lies is full of nutriment of such a mixed character. Moreover, in consequence of the close texture of the membrane, that [25] portion of the sanguineous nutriment will alone filter into it which is of a greasy character; for this portion is composed of the finest particles; and it will be concocted by the heat of the part, and will be converted into suet or lard, and will not acquire a flesh-like or sanguineous constitution. The development, then, of the omentum occurs in this way. But it is used by nature to facilitate and to hasten the [30] concoction of food. For all that is hot aids concoction; and fat is hot, and the omentum is fat. This too explains why it hangs from the middle of the stomach; for the upper part of the stomach is assisted in concoction by the adjacent liver. Thus [35] much as concerns the omentum.

  4 · The so-called mesentery is a membrane; and extends continuously from the long stretch of intestine to the great vessel and the aorta. In it are numerous and [678a1] close-packed vessels, which run from the intestines to the great vessel and to the aorta. The formation of this membrane we shall find to be the result of necessity, as is that of the other parts. What, however, is the cause of its existence in sanguineous [5] animals is manifest on reflection. For it is necessary that animals shall get nutriment from without; and, again, that this shall be converted into the ultimate nutriment, which is then distributed to the various parts; this ultimate nutriment being, in sanguineous animals, what we call blood, and having, in bloodless animals, no definite name. This being so, there must be channels through which the [10] nutriment shall pass, as it were through roots, from the stomach into the blood-vessels. Now the roots of plants are in the ground; for thence their nutriment is derived. But in animals the stomach and intestines represent the ground from which the nutriment is to be
taken. The mesentery, then, is an organ to contain the [15] roots; and these roots are the vessels that traverse it. This then is the final cause of its existence. But how it absorbs nutriment, and how that portion of the food which enters into the vessels is distributed by them to the various parts of the body, are questions which will be considered when we come to deal with the generation and nutrition of animals. [20]

  The constitution of sanguineous animals, so far as the parts as yet mentioned are concerned, and the reasons for such constitution, have now been set forth. In natural sequence we should next go on to the organs of generation, as yet undescribed, on which depend the distinctions of male and female. But, inasmuch as we shall have to deal specially with generation hereafter, it will be more convenient [25] to defer the consideration of these parts to that occasion.

  5 · Very different from the animals we have as yet considered are the Cephalopoda and the Crustacea. For these have absolutely no viscera whatsoever; as is indeed the case with all bloodless animals, in which are included two other [30] genera, namely the Testacea and the Insects. For in none of them does the material out of which viscera are formed exist. None of them, that is, have blood. The cause of this lies in their substance. For the presence of blood in some animals, its absence from others, must be included in the formula which determines their respective [35] substances. Moreover, in the animals we are now considering, none of those final causes will be found to exist which in sanguineous animals determine the presence [678b1] of viscera. For they have no blood-vessels nor bladder, nor do they breathe; the only part that it is necessary for them to have being that which is analogous to a heart. For in all animals there must be some central and commanding part of the body, to lodge the sensory portion of the soul and the source of life. The organs of nutrition [5] are also of necessity present in them all. They differ, however, in character because of differences of the habitats in which they get their subsistence.