THE ALIMENTARY CANAL 



375 



muscular my enteric ganglionic plexus (Auerbach's) for the supply of 

 the muscular coat, and a sub mucous plexus (Meissner's) which sup- 

 plies branches to the blood-vessels and to the glands of the mucosa. 

 The finer branches in the mucous membrane penetrate to the villi, form- 

 ing a delicate plexus of naked fibrils about its blood-vessels and lacteals, 

 and upon its epithelium. 



Intestinal Absorption. The absorption of fat consists essentially 

 of three phases: (1) its absorption into the intestinal epithelium; (2) 



FIG. 348. INTESTINAL MUCOSA OF A FROG DURING THE ABSORPTION OF FAT. 



a, epithelium; 6, tunica propria; c, an ameboid leukocyte. Osmium tetroxid. 

 Highly magnified. (After Schafer.) 



its secretion into the lymphoid tissue of the villus; and (3) it's entrance 

 into the lacteal vessels. In an animal killed during the absorption of 

 fat, the intestinal villi, after fixation by solutions of osmium tetroxid, 

 contain fat in (a) the epithelium, (b) the lymphoid tissue, and (c) the 

 central lacteal. 



In the epithelium, fat is contained in the form of fine droplets 

 which are most numerous in the distal or free ends of the cells. 'They 

 are also found in the intercellular spaces. During absorption the epi- 

 thelial cells of the villi become much swollen and elongated. As the 

 process subsides they return to their former size, and become relatively 

 shrunken. When most distended the intracellular fat droplets are the 



