CHAPTEE XI. 



INTESTINAL DIGESTION. 



Physiological anatomy of the small intestine Size of the small intestine Divi- 

 sions of the small intestine Mucous membrane of the small intestine Yal- 

 vulae conniventes Glands of Brunn Intestinal tubules, or follicles of Lieber- 

 kiihn Intestinal villi Solitary glands, or follicles, and the patches of Peyer 

 Intestinal juice Secretion of the solitary and agminated glands General 

 properties of the intestinal juice Action of the intestinal juice in digestion. 



Physiological Anatomy of the Small Intestine. 



THE small intestine, so called on account of its small size 

 as compared with, the rest of the intestinal tract, is the long 

 cylindrical tube which occupies the greatest part of the 

 abdominal cavity. This must now be regarded as the most 

 important division of the digestive system ; and its physiolo- 

 gical anatomy, together with that of the great glands which 

 discharge their secretions into its cavity, are indispensable as 

 an introduction to the study of intestinal digestion. As it is 

 in the small intestine that the final elaboration of most of 

 the alimentary principles takes place, and here also that these 

 principles are taken into the circulating fluid, we will find, 

 in our study of its anatomy, certain parts which are con- 

 cerned in digestion, and others which, as far as we know, are 

 connected only with the function of absorption. It will be 

 most convenient, however, to consider, in this connection, all 

 the structures found in the small intestine, which possess 

 physiological interest. 



The small intestine, extending from the pyloric ex- 

 tremity of the stomach to the ileo-csecal valve, is held to the 



