PARENTERAL DIGESTION 59 



may exert a more serious action on some of the 

 more distant organs, especially the kidneys. 



During fetal life all the food enters the body 

 parenterally and there is no enteral digestion. 

 There are reasons for suspecting that during 

 infancy the chief milk protein, casein, may be 

 absorbed in part in an unbroken state. At least 

 in a few instances unchanged casein has been 

 detected by the biological test in the blood of in- 

 fants suffering from summer diarrhea. 



In my opinion there are reasons for believing 

 that in some animals a certain part, or certain 

 kinds, of protein food are absorbed unbroken 

 and are digested parenterally. Kabbits are 

 easily sensitized, notably by casein fed by the 

 mouth or administered by the rectum. I have 

 detected the protein in the heart's blood by the 

 biological test after such feedings. While there 

 is a promising field for research along these 

 lines, it is safe to say that in man in health, the 

 amount of unbroken, foreign protein reaching 

 the circulation is small. Protein in appreciable 

 quantities reaches the blood only when injected, 

 as in the employment of sera and vaccines or 

 through infection. In the latter instance the 

 protein multiplies in the body. 



It is evident that one or more of the follow- 

 ing effects may result from the parental intro- 



