HUMAN STRUCTURE AND LIFE- ACTIVITIES 479 



C-J 



400. Digestion in the Intestine. While the gastric juice 

 has power to digest protein foods, the fact is that most of 

 them do not remain in the 



stomach long enough for 

 complete digestion ready 

 for absorption. At inter- 

 vals the muscular ring of 

 the pylorus relaxes and 

 allows partially digested 

 foods to escape into the 

 intestine, there to undergo 

 final digestion and absorp- 

 tion into the blood. This 

 food which escapes into 

 the intestine from the 

 stomach is water contain- 

 ing (1) much starch not 

 digested by the saliva, (2) 

 sugar which was eaten as 

 such and much of the 

 sugar formed by the di- 

 gestion of starch by the &LM 

 saliva, (3) dissolved pro- 

 teins digested in the 

 stomach, (4) many small 

 particles of undigested 

 proteins, (5) fat in liquid FIG. 159. 

 (oil) condition. The work 

 of the intestine is to com- 

 plete the digestion of the 

 proteins, fats, and starch; 

 and to absorb the products of digestion into the blood. 



401. Secretions in the Intestine. These are formed by 

 the pancreas, the liver, and the glands of the intestinal walls. 

 The pancreatic secretion contains enzymes able to digest 



7..tr* 



A, two villi from intestine. 

 Blood-vessels represented by black lines. 

 g .1, intestinal gland ; I, lacteal or lymph- 

 vessel ; B, three cells from covering of 

 villi ; C, two cells from lining of glands. 

 (After Hardy.) 



