112 THE PROTEIN ELEMENT IN NUTRITION 



alkalinity of the liver and other tissues, the metabolism of 

 100 grammes of protein, or 16 grammes of nitrogen, daily would 

 not mean any excessive degree of tissue disintegration and 

 rebuilding. 



In round numbers it would entail an interchange of about 

 1 gramme of protein in every 150 grammes of protoplasm present 

 in the body of the average man. 



Reference has been made to the evidence afforded by the 

 work of Folin, Chittenden, and others, and to the conditions that 

 obtain during under-feeding and starvation. From the results 

 obtained it has been shown that the physiological minimum of 

 nitrogen interchange is reached when the absorption and assimila- 

 tion is decreased to about 6 grammes daily, the heat value of the 

 diet being large and almost entirely derived from carbohydrates 

 and fat. Folin's investigations, on the other hand, would appear 

 to show that endogenous or tissue metabolism of the bod}- is a 

 very trivial affair, requiring, if the creatinine-nitrogen of the 

 urine is any index, an interchange of less than 1 gramme of 

 nitrogen between the tissue cells and lymph. The general effect 

 of these observations would be to show that the average quantity 

 of protein consumed by mankind in his daily fare is far in excess 

 of the true requirements of the body. We have dealt with some 

 of the arguments that have been relied on, and discussed their 

 bearing on the point at issue. The real question to be decided 

 is : Can the body maintain itself in an efficient condition, as 

 regards its physical development, capacity for work, and resist- 

 ance to disease, in as satisfactory a manner on just that quantity 

 of protein that has been shown experimentally to be sufficient, 

 to establish nitrogenous equilibrium at its lowest level, or, are 

 larger quantities of protein, and a higher plane of nutritive 

 changes essential ? 



The question is narrowed down to this : Accepting the view 

 that the energy of muscular contraction can be and is to a 

 considerable extent supplied by non-nitrogenous foodstuffs 

 and the carbohydrate moiety of the protein molecule, are we, 

 therefore, justified in advocating a large decrease in the protein 

 intake as compared with the amount arrived at in standard 

 dietaries ? 



Is the amount of protein necessary for the repair of true 

 tissue waste Folin's endogenous metabolism- and that neces- 

 sary to cover the loss from external secretions, hairs, epithelial 



