176 ORGANIC AGRICULTURAL CHEMISTRY 



lining of the small intestine. Although we shall consider these 

 two digestive juices and the action of their enzymes separately, 

 they act more or less together. 



The chemical reactions taking place when protein food is 

 hydrolyzed by the enzymes of these two juices are of the same 

 nature as those occurring with pepsin, i.e. the protein is hydro- 

 lyzed to amino-acids as the final product. 



Pancreatic Juice. — The pancreatic juice is secreted by the 

 pancreas, a contributory organ which is connected with the 

 small intestine by a duct known as the duct oj Wirzung. This 

 duct opens into the small intestine near the opening from the 

 stomach to the intestine. This opening is known as the pylorus. 



Hormones. — The secretion of the pancreatic juice and its 

 flow into the intestine for the purpose of digesting the protein 

 food, which comes from the stomach, is an exceedingly interest- 

 ing process involving the action of a new class of substances 

 known as hormones. These hormones are similar to enzymes 

 in some respects, but are not destroyed by boihng. In the 

 case of the relation of hormones to pancreatic juice the series 

 of actions has been very thoroughly established, and it will 

 be worth our while to consider them carefully. 



When the food mass has been thoroughly mixed in the stomach 

 by means of the peristaltic action of the stomach muscles, it is 

 finally passed along to the pyloric region of the stomach, where 

 it remains until its acidity reaches a certain point. In this 

 condition the food mass is known as chyme. The opening of 

 the pylorus and the actual passage of the chyme through it 

 is regulated by the acidity of the chyme. When this condition 

 is reached the pylorus opens and the chyme enters the small 

 intestine, which, for the length of about twelve inches, is known 

 as the duodenum (the name signifies twelve). Into this duo- 

 denum the duct of Wirzung opens. In the epithelial cells of 

 the lining of the duodenum is a substance or hormone known 

 as prosecretin. The hydrochloric acid of the chyme hydrolyzes 

 this prosecretin and yields a second hormone known as secretin. 

 This hormone secretin is then conveyed by the blood to the 



