CHAPTER IV 



IN WHAT FORM DOES INGESTED PROTEIN 

 ENTER THE CIRCULATION? 



Our conception of the nature of metabolic processes 

 in the tissues will be more or less modified by the view 

 accepted concerning the degree and character of dis- 

 integration of protein induced in the alimentary tract 

 and the form of the products absorbed. This being so 

 a consideration of the hypotheses that have been ad- 

 vanced relative to the fate of protein after its dis- 

 appearance from the gastro-enteric tract is now in 

 order. This fate of ingested protein has been ex- 

 plained in at least four different ways, namely : 



1. The proteins are absorbed with little or no 

 chemical change and are taken up by the tissues and 

 incorporated into them. In a previous chapter it has 

 been noted that native protein may be absorbed as 

 such at times and fail to reappear leading to the infer- 

 ence of utilization by the tissues. This, however, 

 cannot be accepted as the usual procedure for all the 

 food protein. Once in the blood stream as shown by 

 parenteral introduction protein utilization apparently 

 occurs through the intervention of enzymes which sud- 

 denly make their appearance in the circulation. 



