220 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



membrane of the stomach. Consequently, the solipede has a mucous 

 membrane about twice, and the ruminant about three times, as extensive 

 as its cutaneous surface, while the mucous membrane of the stomach 

 alone of the ox is one and one-half times as extensive as the skin sur- 

 face. In the carnivora— the dog or the cat, for example— the mucous 

 membrane, from the simple character of their food, is very much less 

 extensive in proportion to their external body surface, being only about 

 two-thirds as large as their skin surface. The omnivora, again, occupy a 

 mean between the carnivora and the herbivora. 



The length of the alimentary canal, in a less strict degree, however, 

 is also subordinate to the character of the alimentation. In the herbiv- 

 ora the intestinal tube may be as much as twenty-eight times the length 

 of the body, while the intestinal canal of the carnivora is only three or 

 four times as long as the body. There are, however, many exceptions 

 to this rule. Thus, the dromedary has an intestinal tube only five times 

 as long as its body ; the ram twenty-eight times as long ; the deer twelve 

 times ; the rabbit nine ; elephant seven ; the hyena eight, and the seal 

 twenty-eight times as long as its body length. In these apparent excep- 

 tions, as, for example, in the case of the seal, a carnivorous animal, 

 though there is an intestinal tube twenty-eight times as long as its body, 

 we have the proportion of mucous membrane still preserved ; for, where 

 in herbivorous animals we have a comparatively short tube, its diameter 

 is always proportionately great, while in the case of carnivorous ani- 

 mals, where the tube is long, its diameter is accordingly small. Thus, 

 the alimentary canal of the horse is shorter than that of the ox, the 

 former being about ninety feet ; but it is very much more capacious. 



Change in the normal diet of animals leads to changes in the rela- 

 tive dimensions of their intestinal canals. Thus, the alimentary tube of 

 the wild boar is shorter than that of the domestic hog, since its habit in a 

 state of nature is more carnivorous than in domestication. The domes- 

 ticated cat, living on a mixed diet, has an intestinal tube which is longer 

 than the cat in a state of nature, and the same difference also applies to 

 the domestic ox as contrasted with the buffalo. 



The relative capacity of the alimentary canal is even more strictly 

 definable in different species according to their alimentation. The herbiv- 

 ora always have a greater capacity of intestinal tube than the carnivora. 

 In all cases the volume of the stomach is in inverse proportion to that of 

 the capacity of the intestine. Thus, in the horse the stomach is capable 

 of containing from about sixteen to eighteen litres, while the capacity of 

 the horse's intestine varies from one hundred and twenty-five to three 

 hundred litres. In the ox the stomach contains two hundred litres, the 

 intestine one hundred litres. The value of these differences will be 

 studied later. They serve simply to indicate the immense expanse in 



