192 THE INCOME OF ENERGY 



change starch to sugar or whether it causes the 

 decomposition of other substances. 



Place a small piece of fibrin in a test-tube and 

 add 2 c.c. filtered saliva. Keep the tube several 

 hours at a temperature of 35-40 C. 



The fibrin will not change. 



Place 0.5 c.c. neutral olive oil (page 207) and 2 

 c.c. filtered saliva in a test-tube. 



Noteworthy changes will be absent. 



From these experiments it is evident that 

 diastase decomposes starches, but does not de- 

 compose proteids and fats. Its ferment action is 

 thus far " specific." The belief that each ferment 

 has its own characteristic product will be in- 

 creased by the study of the following typical 

 ferment actions. 



PROTEID DIGESTION BY PEPSIN 



Gastric Digestion of Cooked Beef and Bread. 



At 7 A.M. feed cooked beef and bread to a cat 

 which has fasted twelve hours. At 11 A. M. kill 

 the cat, expose the stomach, and apply double 

 ligatures about 1 cm. apart to the duodenum at 

 the pylorus and to the oesophagus at the cardiac 

 orifice. Eemove the stomach. Open the stomach 

 very cautiously by drawing a knife along the 

 greater curvature. 



" The stomach is very full, and still contains 



