the organs annexed to abdominal digestive canal. 493 



Genekal aot) Comparative Survey of the Abdominal or Essential 

 Portion of the Digestive Tube. 



We have terminated the description of the anatomical characters which 

 distinguish the essential portion of the alimentary canal in all the domesticated 

 animals, and what gradations has this study revealed ! Let us recapitulate and 

 compare them, before showing the admirable harmony which pervades these 

 diverse arrangements, and adapts them to the variations in general organization, 

 habits, and instincts. 



In the Carnivora, which subsist on flesh (Do(/ and Oat), we have seen a 

 very ample stomach, secreting a gastric fluid throughout the whole extent of its 

 mucous membrane, and intestines (relatively) extremely short. 



In the Omnivom, or Mammalia which live on a mixed diet (Fig), we have 

 found a small portion of the internal surface of the stomach occupied by a mucous 

 membrane unfitted to secrete gastric juice, and the intestines relatively of much 

 more considerable capacity than in Carnivora. 



With the Herbivora, which derive their nourishment exclusively from the 

 vegetable kingdom (Ruminants, Rodents, and Solipeds), the surface for the pro- 

 duction of the gastric juice also singularly diminishes in extent, although the 

 stomach in some of these animals is remarkable for its extraordinary development. 

 But to compensate for this, the capacity of the intestinal canal assumes con- 

 siderable proportions, and, in the various species, is in direct inverse relation 

 to the area of the gastric surface. This surface being relatively more extensive 

 in Ruminants than in the Rabbit, and more also in that animal than in Solipeds, 

 all these animals ought to be classed in an inverse order, with regard to the 

 development of the intestinal surface. 



Finally, in considering as the internal surface of the stomach (a point of view 

 quite rational) only those portions of the mucous membrane organized for the 

 secretion of the gastric juice, we are led to recognize that this surface is in 

 inverse proportion to that of the intestine ; that it reaches its highest develop- 

 ment in Carnivorous animals ; and that it is reduced to the smallest dimensions 

 in Solipeds — animals which, on the contrary, present a very great development of 

 the intestinal surface. 



The nature of the aliment readily accounts for these remarkable differences. 

 The Carnivora, living on sul^stantial food, take it in very large quantity, 

 because they are exposed to frequent fastings ; it is, therefore, necessary that 

 they should have a stomach large enough to contain the ingested substances, 

 and to secrete the amount of gastric juice needed to transform them into 

 assimilable materials. If these animals have a short and narrow intestine, it is 

 because a small surface only is required to absorb the products of digestion, these 

 being mixed with but a minimum quantity of non-nutritive substances, and 

 readily come in contact with the absorbing membrane. 



With regard to the Herbivora, their food contains a trifling proportion of 

 nutritive elements in an extremely large bulk of material, and being compelled to 

 ingest great quantities at short intervals, the stomach, properly called, can only 

 be a temporary receptacle for the aliment, which passes rapidly through it after 

 being impregnated by the gastric juice. The surface which secretes that fluid 

 is also singularly reduced, because if it has to perform its functions more frequently 

 than in Carnivora, it is not required to display so much activity in a given time. 

 If, on leaving the stomach, the alimentary matters encounter a vast intestinal 

 34 



