130 



ELEMENTS OF MAMMALIAN ANATOMY. 



The mucous coat of the small intestine contains tube- 

 like glands, the glands of Ljeberktihn, whose secretion 

 changes starch into sugar. In the duodenum and 

 jejunum the mucous membrane is thrown into numerous 

 transverse folds, vahuli conniventes, which increase the 

 surface for absorption. The villi are minute finger-like 

 processes (Fig. 62), barely apparent to the naked eye, 

 projecting into the lumen for the purpose of absorbing 

 the nutriment from the chyle. They consist of a covering 



of columnar epithelial cells (Fig. 

 63), within which ends a chyle ves- 

 sel or lacteal surrounded by small 

 blood-vessels held in place by con- 

 nective tissue. The fatty portions 

 of the food are carried by the lac- 

 teals (Fig. 78) to the left thoracic 

 duct, and thence to the jugular vein, 

 while other portions of the food are 

 taken up by the capillaries of the 

 portal system, which begin in the 

 villi (Fig. 63). The mucous mem- 

 brane of the large intestine like- 

 wise contains tube-like glands sim- 

 ilar to the glands of Lieberkiihn, 

 but no villi. 



The submucous or areolar coat is adjacent to the mucous 

 coat of the intestine, but in the stomach the muscularis 

 mucosae intervenes. Next to the submucous coat is 

 the muscular coat, composed of two layers, one of circular 

 fibers, the other of longitudinal fibers. An additional 

 layer of oblique fibers is present in the cardiac end of 

 the stomach, which aid in giving that organ the peculiar 

 churning or peristaltic motion necessary for chymifica- 

 tion of the food. A fourth coat or serous covering sur- 



FIG. 62 CROSS-SECTION 

 OF THE SMALL INTES- 

 TINE. X 5. 



ex, Longitudinal muscular 

 coat ; m, circular muscu- 

 lar coat; mu, mucous 

 coat; Ib, glands of Lie- 

 berkuhn; se, serous or 

 peritoneal coat ; sm, 

 submucous or areolar 

 coat. 



