have it large; those which are omnivorous (as the black rat) have it small; while in those which feed on succulent vegetables (as the hare) it is exceedingly large, having ten times the dimensions of the stomach.
In man the cæcum is tolerably large and globular, with a "vermiform " elongation, found also in certain large apes, and in the wombat. The cæcum is in larger proportion with infants than in adults. Moreover, the human colon is cellulated, as in the herbivora.
In answer to the general statement that the cæcum is larger in the herbivora than in the carnivora, Dr. Tyson states that the hedgehog, which he supposes to be frugivorous, has neither colon nor cæcum. But it is well ascertained that this animal naturally feeds on serpents and on insects. Dr. Tyson also alleges that the opossum, being carnivorous, has both a colon and a cæcum. To this, however, it may be replied that the opossum lives chiefly on roots and wild fruits, though it also devours poultry.
Liver.—The carnivora and rodentia have a very complex liver, consisting of five parts, but in the whole animal series the liver is greater where the lungs are smaller. The liver is less developed in man than in many other mammalia, but more in Europeans and other flesh-eaters than in the inhabitants of warm climates.
Perspiratory Glands.—The herbivora and man have an immense number of perspiratory glands in the skin, by which superfluous heat escapes. The carnivora, eating lean meat, which supplies no abundance of animal heat, are deficient in these glands. It is well known that the dog perspires chiefly from the tongue.
On a general review we find man to resemble the herbivora, in the absence of claws and tusks; in the shape of the teeth; in the joint of the lower jaw; in the form of the cheek-arch, and moderate force of the muscles which chew; in the considerable length of the alimentary canal; in the size and complexity of the other digestive organs, and in the number of the perspiratory glands. In the enamel of the molar teeth being confined to the outside, man agrees with the carnivora. His stomach also is less complex than in most of the herbivora. Yet the horse has a simple stomach and rather short canal, as said above.
But here is a point of some importance. Dr. Combe has observed on a prevalent error, that flesh needs less digestion and therefore flesh-eaters have simpler and shorter digestive organs. But the intestines of grain-eating birds scarcely exceed in length those of rapacious birds. Grain and flesh alike contain much nourishment in small bulk; that is why the creatures which live on these do not need capacious digestive organs. But when the food contains little nourishment in great bulk, the organs must be large and have a large surface to supply digestive juices.
