228 THE HUMAN MECHANISM 



the greater protein consumption. Instead of storing the 

 additional food protein or even part of it over any great 

 length of time, the body soon comes to destroy all the pro- 

 tein eaten. It is for this reason that while animals may be 

 fattened to a remarkable extent by proper feeding, it is not 

 possible to secure a corresponding increase of protein material 

 of the muscle, or lean meat. The accumulation of protein is 

 self-limited. 



In two physiological states the increase of protein is much 

 more marked; namely, during growth and during convales- 

 cence from wasting disease (or after a period of prolonged 

 fasting). It would seem that there is a certain maximum 

 content of protein-like substances in the cell, and that it is 

 not possible by the most abundant feeding to increase 

 this amount. 



It follows from the above that very abundant protein 

 feeding must result in the production of increased protein 

 waste within the body. In the first place, the greater the 

 quantity of protein fed, the greater will be the microbic 

 destruction of protein within the intestine and especially in 

 the large intestine. Not only is the protein so destroyed 

 largely useless to the body, but, in so far as its microbic 

 destruction involves putrefactive changes, harmful products 

 may be formed from it. In the second place, that portion of 

 the protein which escapes microbic action and is absorbed 

 into the blood in the form of digestive products (amino-acids 

 and peptids) disintegrates in the cells with the formation of 

 wastes. Both these processes increase the amount of waste 

 to be eliminated, chiefly by the kidneys. It has been urged 

 that this overburdens the kidneys and causes disease of 

 these organs. While convincing proof has perhaps not been 

 given that a healthy kidney may be injured in this way, 

 it is certain that a diseased or even a temporarily impaired 

 kidney may suffer when such excessive work is thrown 

 upon it. 



