FEEDS AND FEEDING. 395 



poultaceous by the gastric juice as a whole, but, by the 

 chemical ferment, pepsin, the insoluble protein is 

 changed into soluble peptone. 



5. Chylification or intestinal digestion. This step 

 has reference to the food in the small intestine being 

 converted into chyle, which is the nutritive materials, 

 in liquid form, ready for absorption into the circula- 

 tion. After reaching the small intestine, the food ma- 

 terials are again acted upon by ferments which have a 

 somewhat similar action to those already spoken of in 

 connection with the saliva and the gastric juice. These 

 ferments are chiefly from the pancreas, or '* sweet- 

 bread," and are conveyed to the intestine, as a part of 

 the pancreatic juice, through the pancreatic duct or 

 tube. 



These ferments alluded to are: 



(a) Amylopsin, which changes the insoluble starch 

 into soluble sugar. 



(b) Trypsin, which converts insoluble protein into 

 soluble peptone. 



(c) Steapsin, which emulsifies the fats and oils in the 

 food, and renders them more easy of absorption into 

 the circulation. 



6. Absorption. This is the step by which the nu- 

 trient materials of the food, in liquid form, are taken 

 from the alimentary canal into the circulation to be 

 carried by the blood to all parts of the body to nourish 

 the different tissues. And no food is capable of being 

 absorbed until it has first been rendered soluble by the 

 action of the different ferments. 



The sugar (carbohydrate) and the peptone are ab- 

 sorbed by the small veins in the walls of the stomach 

 and intestines, while the emulsified fats are absorbed, 

 mainly, by the lacteals small beginnings of the lym- 

 phatic system distributed to the small intestine. 



7. Circulation. This step is accomplished by the 

 blood in the arteries carrying the nutritive materials, 

 absorbed from the food, to all parts of the body. 



8. Assimilation. This step is undertaken by the 



