188 PHYSIOLOGICAL CHEMISTRY 



Hippuric acid is found in large amounts in the urine of her- 

 bivora. Less than a gram a day usually is present in the urine 

 of man. It is interesting, for it is a substance formed by the 

 union of benzoic acid and glycocoll. The former may be formed 

 in the body, or may be ingested with the food, as it occurs in 

 various fruits and vegetables, particularly in cranberries. The 

 formation of hippuric acid apparently is a protective measure, 

 as benzoic acid is considerably more toxic than hippuric. The 

 benzoic is conjugated with glycocoll, which comes in part from 

 the destruction of protein tissue or food, but also may be synthe- 

 sized by the body. The hippuric acid is then excreted, and the 

 more dangerous benzoic acid thus removed. 



Ammonia. The urine always contains small amounts of am- 

 monia, usually less than a gram a day. Ammonia is used by the 

 body to neutralize acids which are not oxidized and destroyed 

 by the body. The taking of a mineral acid thus will cause an in- 

 crease in urinary ammonia. This occurs also in diabetes, where 

 aceto acetic acid and /?-oxybutyric acid are produced and not 

 further oxidized in the organism. They are excreted in the form 

 chiefly of their ammonium salts. The source of the ammonia is 

 largely the split-off amino groups liberated in the destruction of 

 amino acids when proteins are destroyed. Most of this ammonia 

 is built into urea, but a portion is excreted as such. For the 

 quantitative estimation of ammonia, see the laboratory direc- 

 tions. 



Creatinine and Creatine. 



HN = O 



HN = 



H,N C OH 



N CH 9 HN== 



t 



CH 3 N CH 2 



Creatinine 



CH 8 

 Creatine. 



Creatinine and creatine are two closely related compounds 



