PROTEIN AND CIRCULATION 63 



organism's requirements. The necessity for prelimi- 

 nary extensive disintegration of the food protein has 

 been offered as follows : "Every species of animal in 

 fact every individual has its specifically constituted 

 tissues and cells. If the diet was always the same, the 

 formation of the tissues might bear some close relation 

 to the components of the food. The diet varies, how- 

 ever, and, especially in the case of human beings and 

 the omnivora, is exceedingly diverse in nature and to 

 make its organism independent of the outer world in 

 the matter of food taken, it disintegrates the nutrient 

 it receives, and utilizes those components which may be 

 of service to it in building up new complexes." 



Objections to this theory have been summarized by 

 Cathcart as follows : "The view that the tissue proteins 

 differ from one another, that they are specific bodies 

 of definite constitution, and that, therefore, each re- 

 quires a different amount and supply of building mate- 

 rial is gradually being accepted. Abderhalden himself 

 accepts this. What end then is served in having a 

 single uniform pabulum formed when the demand is 

 so varied? This is all the more questionable when it 

 is remembered that there is no indubitable evidence 

 which shows that one amino acid can be converted 

 into another. Further, the belief is gradually gaining 

 ground, as regards the protein requirements of the 

 organism, that it is not so much the actual quantity as 

 the quality of the protein supplied in the food, which 

 is of importance. If the material supplied be uniform 

 it necessitates a fresh breakdown by each tissue, 



