WEAR AND TEAR QUOTA, SPECIFIC DYNAMIC ACTION. 



plete nitrogenous equilibrium on a much greater nitrogen supply. The 

 protein minimum also seems to vary in different individuals. 



The protein minimum can also be different for other reasons. It 

 varies, as mentioned by RUBNER, not only with the kind of foodstuffs, 

 but also with the nutritive condition of the body. The needs of the 

 cells for protein varies with the nutritive condition of the body. Where 

 the protein is eagerly demanded, less supply of protein suffices, and where 

 the demand is low more protein must be offered (RUBNER) . The more the 

 body has become reduced the lower is the protein minimum, according to 



RUBNER. 1 



As mentioned in the early part of this chapter, the body always suffers 

 a certain loss of nitrogen through the falling out of the hair and other 

 epidermis formations, by the secretions, etc.; but to this also belongs che 

 constant loss of nitrogenous substance which every cell sustains because 

 of its activity. This unpreventable loss of nitrogen has been included 

 by RUBNER under the name " wear and tear " quota, and this quota, 

 which corresponds to the nitrogen elimination with a perfectly nitrogen- 

 free diet, and hence is a protein minimum, may rise to 4 per cent of 

 the total calorific needs. The energy supply of the food is under these 

 conditions entirely assumed by the non-nitrogenous foodstuffs. 



All proteins do not have the same value in replacing the protein 

 minimum. MiCHAUD 2 determined the protein minimum in dogs by 

 feeding entirely with nitrogen-free food, and he found that this min- 

 imum can be covered by the corresponding quantity of protein specific 

 of the animal, but not by the same quantity of a foreign protein, like 

 gliadin and edestin. 



The purposes of the protein as foodstuff are, according to RUBNER, as 

 follows: (1) To compensate for the wear and tear quota ; (2) betterment 

 of the condition of the cells; and (3) dynamogenic purpose. In the 

 accomplishment of this third purpose the protein splits into a nitrogenous 

 and a non-nitrogenous part. The potential energy set free immediately 

 as heat in the combustion of the nitrogenous part, which is quantitatively 

 used within the region of the chemical heat regulation but is otherwise 

 lost, has been called the specific dynamic action by RUBNER. S The 

 remainder of the energy which is represented by the non-nitrogenous 

 part of the proteins, serves, like all other foodstuffs, in satisfying the 

 energy requirement of the cells. According to RUBNER only non-nitrog- 

 enous groups (of the proteins, fats and carbohydrates) come almost 

 entirely, if not completely, in consideration for purposes of energy. 



1 Rubner, Theorie d. Ernahrung nach Vollendung des Wachstums, Arch. f. Hyg., 

 66. 1-80 and Ernahrungsvorgange beim Wachstum des Kindes, ibid., 66, 81-126. 



2 Zeitschr. f. physiol. Chem., 59. 



3 Rubner, 1. c., and Gesetze des Energieverbrauches, 70. 



