WORKING OVER THE BODY'S INXOME 135 



from the stomach without being digested by the pepsin, will 

 now be digested by the action of the pancreatic ferments. 

 3. A ferment that breaks up fats into glycerin and fatty acids. 

 The latter combine with other substances to make soaps. Soaps 

 and glycerin dissolve 

 in water and diffuse 

 through the cell walls. 

 Pancreatic juice thus 

 contains the ferments 

 necessary for digesting 

 all nutrients. 



113. The liver. This 

 produces bile or gall. 



1. Bile contains no 

 digestive ferments, but 

 it does influence the 

 absorption of the fatty 

 acids and soaps by the 

 cells of the intestine. 



2. The bile seems to 

 have some effect upon 

 the activity of the pan- 

 creatic ferments. When 

 the contents of the 

 stomach pass into the 

 intestine, the mixture is 

 acid. The bile neutral- 

 izes the acid and makes 

 possible the activity of 

 the other ferments. 



3. The bile is made up chiefly of materials that are of no fur- 

 ther use to the body ; the liver is thus also an excretory organ. 



114. The intestinal juices. The juices secreted by the glands of the 

 intestine contain no ferments of great importance in digestion, but they 

 neutralize the acids resulting from various chemical changes in the gut. 

 One ferment in the intestinal juice converts cane sugar into simpler sugars. 



Fig. 77, Lining of the intestine, (x 150) 



The tiny projections from the lining of the small 

 intestine, the villi, give the appearance of very 

 fine velvet. Absorption takes place through the 

 outer layer of cells. Within each villus are fine 

 blood vessels and lymph spaces ; from these the ab- 

 sorbed food is transferred to the circulation sys- 

 tem. Chemical changes take place in the course of 

 the transfer. As a result the material taken into 

 the blood is not exactly the same as that absorbed 

 from the intestine, although it is made up of the 

 same elements 



