The belly and the intestines are covered with a caul known as the “omentum,” consisting of a fatty, thin membrane; except in the case of those animals which are oviparous. To this membrane is attached the spleen, which lies on the left side, and opposite the liver: sometimes, indeed, it changes place with the liver, but such a case is looked upon as nothing less than a prodigy. Some persons imagine that a spleen of extremely diminutive size exists in the oviparous animals, as also in serpents; at all events, it is to be detected in the tortoise, the crocodile, the lizard, and the frog; though it is equally certain that it does not exist in the bird known as the “ægocephalos,”[298] nor yet in those animals which are destitute of blood. The spleen sometimes offers a peculiar impediment in running, for which reason the region of the spleen is cauterized[299] in runners who are troubled with pains there. It is said also, that if the spleen is removed[300] by an incision, animals may survive. There are some persons who think that with the spleen man loses the power of laughing, and that excessive laughter is caused by the overgrowth of it. There is a territory of Asia, known as Scepsis,[301] in which it is said that the spleen of the cattle is remarkably small, and that from thence it is that remedies for diseases of the spleen have been introduced. CHAP. 81.—THE KIDNEYS: ANIMALS WHICH HAVE FOUR KIDNEYS. ANIMALS WHICH HAVE NONE. About Briletum and Tharne[302] the stags have four kidneys: while, on the other hand, those animals which have wings and scales have[303] none. The kidneys adhere to the upper part of the loins. Among all animals, the kidney on the right side is more elevated than the other, less fat, and drier. In both kidneys there is a certain streak of fat running from the middle, with the sole exception of those of the sea-calf. It is above the kidneys, also, that animals are fattest, and the accumulation of fat about them is often the cause of death in sheep. Small stones are sometimes found in the kidneys. All quadrupeds that are viviparous have kidneys, but of those which are oviparous the tortoise is the only one that has them; an animal which has all the other viscera, but, like man, has the kidneys composed, to all appearance, of several kidneys, similar to those of the ox. CHAP. 82.—THE BREAST: THE RIBS. Nature has placed the breast, or, in other words, certain bones, around the diaphragm and the organs of life, but not around the belly, for the expansion of which it was necessary that room should be left. Indeed, there is no animal that has any bones around the belly. Man is the only creature that has a broad breast; in all others it is of a carinated shape, in birds more particularly, and most of all, the aquatic birds. The ribs of man are only eight in number; swine have ten, the horned animals thirteen, and serpents thirty. CHAP. 83.—THE BLADDER: ANIMALS WHICH HAVE NO BLADDER.