DIGESTIVE SYSTEM IN MAN 85 



at a time. This movement is called peristalsis and is very 

 similar to the swallowing movement of the gullet. 



When a food mixture passes from the stomach, it contains 

 all of the fat that it contained when it first entered the mouth, 

 since neither the saliva ferments nor the gastric ferments have 

 any effect upon fats. It contains all the sugar that was there to 

 begin with, together with all the sugar that was formed by the 

 digestion of starch in the mouth. It contains whatever starch 

 was not digested. It contains the peptones formed by the gas- 

 tric digestion (in solution), and particles of proteins that were 

 not digested. In addition there is a quantity of water, mineral 

 salts, the remains of the gastric and salivary juices, and the 

 fibers and cell walls of the food material, which have not becK 

 acted upon in the mouth or in the stomach. In the intestines 

 many changes take place in the character and composition of 

 this mixture. 



Near the beginning of the intestine (Fig. 28, //, /) there is a 

 small opening connected with two small tubes, or ducts. One 

 of these is connected with the largest gland in the body, the 

 liver \ the other is connected with another very important 

 gland, the pancreas (Fig. 28, 0). 



120. The pancreas. The juice secreted by the pancreas 

 contains three important kinds of ferments : 



1. A ferment that converts starch into sugar. 



2. A ferment that digests proteins into simpler compounds. 



Any starch that has been swallowed before the saliva has had time 

 to transform it into sugar, and any protein that has passed from the 

 stomach without being digested by the pepsin, will now be digested 

 by the action of the pancreatic ferments. 



3. A ferment that acts upon the fats in the food, breaking 

 them up into glycerin and fatty acids, which latter combine 

 with other substances to form soaps. 



The soaps and the glycerin dissolve in water and diffuse 

 through cell membranes. 



