350 STUDIES IN ADVANCED PHYSIOLOGY. 



juice. It is desirable to point out again that this change of 

 the sugars does not occur in the contents of the intestine. 

 The intestinal juice is too scanty to have much effect there, 

 but occurs while the sugars, which are quite dialyzable, are 

 in the act of passing through the intestinal wall. Here in 

 the mucous membrane moistened with the intestinal juice, 

 cane sugar, maltose and lactose are changed into glucose, 

 and in that form all the carbohydrates eaten reach the 

 blood. 



GENERAL SUMMARY. 



First. The proteids are not affected by the saliva. By 

 the gastric juice they are more or less completely changed 

 into peptones, and by the pancreatic juice the change from 

 proteids into peptones is made complete, save that in the 

 pancreatic digestion some of the peptones are digested still 

 further into compounds called leucin and tyrosin. 



Second. The albuminoids are not affected by the saliva 

 but digested by the gastric juice, and the digestion when 

 incomplete completed by the pancreatic juice. 



Third. The starches are acted upon by the ptyalin of 

 the saliva and partially changed into maltose. In the 

 stomach all action upon the carbohydrates is suspended. 

 In the intestine the ptyalin renews its action, but is aided 

 by the amylopsin of the pancreatic juice and so all the 

 starches are changed into maltose. This maltose, then, 

 together with the cane sugar taken in the food and the lac- 

 tose from the milk, is changed by the intestinal juice into 

 glucose or grape sugar, in its passage through the walls. 



Fourth. The fats are not acted upon by the saliva and 

 are not directly affected by the gastric juice either except 

 to be liberated when surrounded with albuminous envel- 

 opes, but in the intestines they are saponified by the steap- 

 sin and emulsified by the soap so produced, and by the 

 bile. 



Fifth. A number of mineral substances insoluble in 

 water are dissolved in the free hydrochloric acid of the 

 stomach, and in solution reach the blood. At the end of 



