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THE HUMAN BODY 



The digestive enzyms of the succus entericus are four; one pro- 

 teolytic, erepsin, which acts particularly on proteoses and pep- 

 tones, thus completing the work of the gastric pepsin; and three 

 so-called inverting enzyms, which change double sugars to single 

 sugars. These enzyms are specific in their action, each affecting 

 only its particular sugar. Maltose inverts maltose, thus com- 

 pleting the starch digestion begun by ptyalin and amylopsin; 

 sucrase splits cane-sugar or sucrose, and lactose converts milk-sugar, 

 lactose, to single sugar. The result of the action of these three en- 

 zyms is to bring all the carbohydrates of the food, except cellu- 

 lose, into the condition of single sugars, in which form they are 

 ready for the use of the Body. 



Summary of the Digestive Process. The chemical reactions by 

 which the various food stuffs are made ready for absorption and 

 use by the Body can be conveniently summarized in tabular form : 



1 Intermediate products. 



2 Final products. 



Bacterial Digestion. The human intestines normally contain 

 enormous numbers of bacteria. In the small intestine the action 

 of these is for the most part fermentation of carbohydrates with 

 the production of carbon dioxid, alcohol, and acetic and lactic 

 acids. There is no doubt that even in perfect health a considerable 

 fermentation goes on in the intestine. So far as appears it is 



