LENGTH OF INTESTINE IN MAMMALS. 585 



partments, two being cardiac pouches, and also three rows of large crypts 

 along the bands. 



It is remarkable that the carnivorous Cetacea have a more complex stomach 

 than the herbivorous species. In the dugong, amongst the latter, this organ 

 is elongated, and marked off into a cardiac and a pyloric portion, by a con- 

 striction, from near which two blind pouches proceed ; the cardiac pouch pre- 

 sents a large glandular surface. The carnivorous cetacean stomach possesses 

 from three to seven cavities, the first of which has a thicker epithelium than 

 the rest. 



On taking a general view of the above described modifications of the mam- 

 malian stomach, it would seem that, in its simplest form, it is a specially di- 

 lated part of the alimentary canal, distinguished by its abundant glandular 

 tubules ; this becomes elongated and narrower at a certain part, next con- 

 stricted, and then partially subdivided within, by internal folds. These sub- 

 divisions in the complex stomach become still more pronounced, and associ- 

 ated with important differences of structure in the various coats, especially in 

 the lining membrane. The pyloric portion of even the simplest stomach has 

 larger gastric glands than the cardiac portion ; and, in the compound stom- 

 achs, this part alone presents gastric tubuli, and secretes gastric juice. The 

 cardiac end, variously subdivided and modified, is often lined by a thicker 

 epithelium, and has been regarded as a dilatation of the esophagus. 



The intestinal canal is, in all Mammalia, marked off from the stomach by a 

 circular muscular rim or pyloric valve. It presents even greater varieties 

 than the gastric cavity, and these are more immediately referable to the 

 nature of the food. 



The most noticeable difference is in the relative length of the intestines, from 

 the pylorus downwards, which are nearly always shorter in the flesh-feeding, 

 and longer in the vegetable-feeding species, in every Order. The following 

 Table illustrates both the rule and the exceptions : 



Flesh- Feeders. Vegetable-Feeders. 



Carnivora Kuminantia 



Cat, dog, . . . 5 to 1 Sheep, . . . . 30 to 1 



Bear, hyena, . 9 or 8 to 1 Solipeds 



Seal, . . . . 15 to 1 Horse, . . . 20 or 15 to 1 



Insectivora, . . 6 or 3 to 1 Cheiroptera 



Cheiroptera Frugivorous pteropus, 7 to 1 



Insectivorous bats, . 2 to 1 Quadrumana 



Omnivorous, . . 8 or 3 to 1 



Excepting in the Cetacea, and a few Edentata and Cheiroptera, the subdi- 

 vision into a small and large intestine prevails throughout. According to its 

 length, the small intestine is more or less convoluted ; it usually has internal 

 valvular conniventes, and a villous mucous membrane ; villi are always want- 

 ing in the large intestine. At the junction of the small with the large intes- 

 tine, a more or less perfect ileo-ca3cal valve is found, except in the Monotre- 

 mata, Cetacea, and certain Edentata and Cheiroptera. 



The colon is usually speculated. A caecum nearly always exists, its pres- 

 ence and size corresponding closely with the nature of the food, being either 

 absent or small in flesh-feeders, and highly developed in vegetable-feeders. It 

 is absent in all Insectivora and Cheiroptera, in some of the Edentata, and in 

 certain Cetacea. In the Carnivora, generally, it is short and narrow, and is 

 absent in the bears and weasels. It is present, and of variable length, in the 

 Quadrumana. In all Ruminants it is capacious, but is still larger in the 

 Solipeds, being, in the horse, three times as large as the stomach, and meas- 

 uring two feet in length. In the Pachyderms, it is somewhat smaller, but the 

 hyrax has two caeca. Amongst the Bodentia, the caecum is absent in the in- 

 sectivorous dormouse, short and small in the omnivorous rat ; but it attains 

 its greatest size, and is even marked by circular or spiral folds, in the herbiv- 

 orous genera, as in the rabbit and hare, being, in the latter, eight times as 

 capacious as the stomach. In the carnivorous Cetacea, there is .usually no 

 caecum, but the balsena has a small one ; in the herbivorous species, this part 



