INFLUENCE OF FOOD ON THE METABOLISM 



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could be nourished exclusively with proteids. But the capabilities of the digest- 

 ive organs must be considered. In man they are not able to digest and absorb 

 proteid enough to maintain the body; hence man is always compelled to eat 

 nonnitrogenous foodstuffs in addition to proteid. 



A. INFLUENCE OF THE QUANTITY OF PROTEID IN THE FOOD ON 

 PROTEID METABOLISM 



This exceptional position of proteid prompts us to discuss the conditions 

 of its metabolism first. Let us begin by inquiring how the quantity of proteid 

 supplied to the body affects the proteid destruction therein. The following 

 summary of a series of experiments by Bischoff and Voit may serve to give 

 us our bearings. The animal received nothing but meat, which was carefully 

 freed of fat, bones, cartilage, etc. The percentage of nitrogen in the meat 

 is estimated at 3.4 per cent (corresponding to about twenty-one per cent 

 of proteid). 



From this and other similar series of experiments it follows without ques- 

 tion : ( 1 ) that increasing the supply of proteid increases its destruction in 

 the body; (2) that the entire supply of proteid, or, when it is large, almost the 

 entire supply, is destroyed; and (3) that proteid is retained in the body (cf. 

 numbers 1, 9, 10) only when fed in very large quantities. 



