Aristotle

by Various Works [lit]

  to facilitate the concoction of the food, some of them, as the

  Cestreus (mullet), have a fleshy stomach resembling that of a bird;

  while most of them have numerous processes 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 contrast

  between fishes and birds in the position of these processes. For in

  fishes they are placed 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 processes 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 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.

  It has already been mentioned that in animals with front teeth in

  both jaws 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, and smooth on the internal

  surface.

  Not much larger, I say, than the gut; 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 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 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,

  animals of no small bulk, because of the thorough elaboration which

  their food undergoes. The gut, except in those animals where it is

  straight, invariably widens out as we get farther from the stomach and

  come to what is called the colon, and to a kind of caecal

  dilatation. After this it again becomes narrower and convoluted.

  Then succeeds a straight portion which runs right on to the vent. This

  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 to their large size, or to the heat of the parts

  concerned, require more nutriment, and consume more fodder than the

  rest.

  Neither is it without a purpose, that, just as a narrower gut

  succeeds to the upper stomach, so also does the residual food, when

  its goodness is thoroughly exhausted, pass from the colon and the

  ample space of the lower stomach into a narrower channel and into

  the spiral coil. For so 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 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 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 such animals as we are now considering, there is found

  what is called the jejunum; which is a part of the small gut, of the

  gut, that is, 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 residual matter, which by the time it

  has got here has become worthless. There is a jejunum in all these

  animals, but it is only plainly discernible in those of large size,

  and this only when they have abstained from food for a certain time.

  For then alone can one hit on the exact period when the food lies

  half-way between the upper and lower cavities; a period which is

  very short, for the time occupied in the transition of food is but

  brief. In females this jejunum may occupy any part whatsoever of the

  upper 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 reed, but is found in the cavity which separates

  this terminal one from the two 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. It is this

  difference in thickness which makes the milk of horned animals

  coagulate, 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, but also for such apodous 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 gills in its place. None of these animals,

  excepting the tortoise, as also no fish, has a urinary 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 excretion

  when voided throws down a deposit of earthy brine in the containing

  vessel. For the sweet and fresh elements, being light, are expended on

  the flesh.

  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 animals that have teeth in front of both jaws; and

  their viscera are excessively small, as always happens when there is

  no bladder. In serpents these viscera are, moreover, 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.

  All animals that have blood possess an omentum, a mesentery,

  intestines with their appendages, 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.

  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 in some, as in the Amia, 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 when it

  is congealed, and restoring it to cheerfulness when it again flows

  free. But this cannot be. For in some animals there is absolutely no

  gall-bladder 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, of purely sea-animals,

  in the dolphin. Even within the limits of the same genus, some animals

  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 how the existence of this

  part in the whole genus has been a matter of dispute. For each

  observer, according as he has found it present or absent in the

  individual cases he has examined, has supposed it to be 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 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, 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 spirts 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 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 product of decay, so also when it is present in the

  region of the liver it is equally excremental and has no further

  use; just as is the case with the dejections 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 in the body of this

  or that constituent, with such and such properties, many results

  must ensue merely as necessary consequences of these properties. All

  animals, then, whose 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, 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

  serves for the excretion of its impure residue. 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 blood is sweet. So

  that it is evident that the bile, which is bitter, cannot have any

  use, but must simply be 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 the fact, such as the camel and the dolphin;

  and these also are, as it happens, long-lived. Seeing, indeed, that

  the liver is not only useful, but a necessary and vital part in all

  animals that have 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 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 nece
ssary parts of an animal. It is the liver therefore that alone

  has this provision. In conclusion, wherever we see bile we must take

  it to be excremental. For to suppose that it has one character in this

  part, another in that, would be as great an absurdity as to suppose

  mucus or the dejections of the stomach to vary in character

  according to locality and not to be excremental wherever found.

  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 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. Thus attached, it covers the rest

  of the stomach 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 solid and fluid 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 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 when it

  has so filtered in, 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 is simply the result of necessity. But when once formed,