HIPPURIC ACID 205 



is the end product of the destruction of certain materials in the 

 nuclei of cells has considerable support. 



Hippuric acid exists in the urine as hippurates. It differs 

 from most of the other urinary constituents in being formed in 

 the kidney; it does not preexist in the blood. The daily output 

 of this substance is about 10 grains, though the amount may be 

 considerably increased on a vegetable diet. The benzoic acid 

 of vegetables seems to be synthesized into hippuric. In proteid 

 dissimilation some benzoic acid may be produced and eliminated 

 in this shape. 



The various lactates are not formed by the kidney, but pass 

 unchanged into it from the blood. The lactic acid from which 

 they are formed probably results from the transformation of 

 dextrose. 



Creatinin is normally present in the urine. It is a nitrogenous 

 body differing from creatin only by a molecule of water. It is 

 eliminated to the extent of about 15 grains per day. A part 

 comes from proteid destruction in the body, and another part 

 is said to come directly, without metabolism, from creatin which 

 is a constituent of ordinary meat. It is not formed in the 

 kidney. 



Xanthin, hyp oxan thin, etc., are to be regarded as nitro- 

 genous excreta allied to uric acid and resulting in some way 

 from proteid metabolism. They are regarded by some as hav- 

 ing the same probable origin as uric acid, viz., the disintegration 

 of cell nuclei. 



The non-nitrogenous constituents scarcely deserve separate 

 mention. It is through the kidney that the largest variety 

 of these materials are discharged. Certain of these are 

 constant, but the wide variety of such materials taken into the 

 alimentary canal accounts for the same wide variety in the urine. 

 The proportion of inert substances in the blood is approximately 

 constant kept so by the removal of any excess by the kidneys 

 chiefly. 



