THE METABOLISM OF PROTEIN 655 



increase did not bear any relationship to the acid-absorbing power of 

 the blood plasma (see page 650). 



The importance of the kidneys in removing the urea from the blood 

 is readily seen from the change in the percentage of urea in this fluid 

 after the partial or complete removal of the kidneys. Animals sur- 

 vive nephrectomy for about three days, and during this time urea rapidly 

 accumulates in the blood and begins to make its appearance in the 

 saliva and the intestinal secretions. In man also where the kidneys 

 are extensively diseased, a similar accumulation of urea occurs in the 

 blood, some of the excess being got rid of through the sweat and to a 

 certain extent through the intestine. The importance of encouraging 

 perspiration and a free movement of the bowels in cases of nephritis is 

 thus indicated. It must not be concluded that the accumulation of 

 urea in the organism is the direct cause of the symptoms. Urea itself 

 is comparatively inert, and it is generally believed that other metabolic 

 products with which the urea runs parallel in amount are the toxic 

 agents. Hewlett has found, however, that very large injections of urea 

 cause certain symptoms. 34 



