THE URINE 



383 



Of the total organic substance in the urine, urea, creatinin, ammonia, 

 uric acid and purin bases together constitute seventy-five per cent, but they 

 contain ninety-three per cent of the total nitrogen of the urine (Donze and 

 Lambling). 



7. Oxalic acid occurs in very slight traces. 



8. Hippuric acid (Fig. 142), benzoyl-glycocoll (page 378) occurs in con- 

 siderable quantity in the urine of herbivorous animals and in smaller quan- 

 tity in the urine of man. In the latter on ordinary diet it amounts to only 

 about 0.7 g. per day; after a plentiful quantity of vegetable foods it may 

 reach 2 g. or more per day. 



9. The ethereal sulphates and the aromatic oxyacids already mentioned 

 at page 379. The quantity of the former per day in the urine of man is only 

 about 0.09-0.62 g. ; the oxyacids amount to about 0.03 per day. 



10. Among the pigments of the urine the iron-free, nitrogenous urochrome, 

 carefully studied by Garrod, is the most important. Besides, there are present 

 in normal urine: the red pigment uroerythrin, hcematoporphyrin (in very 

 small quantities), and urobilin, first described by Jaffe. The latter has a 

 red or reddish-yellow color, and in the opinion of many authors is identical 

 with hydrobilirubin (C 32 H 40 N 4 7 ) ; but this is contested by others on the 

 ground that hydrobilirubin contains twice as much nitrogen as urobilin. 



FIG. 141. FIG. 142. 



FIG. 141. Still other forms of uric-acid crystals, after Funke. The "wheat stone" and 

 "sheaf" crystals especially are shown. Some of them were found ready formed in 

 urinary sediments; others were obtained by treatment of ordinary sediments containing 

 sodium urate with acids. 



FIG. 142. Hippuric-acid crystals, obtained from human urine by recrystallization from a water 

 solution, after Funke. 



Sterkobilin (cf. page 295), on the other hand, has exactly the same composition 

 as urobilin. At all events urobilin, as well as other pigments, probably stands 

 in a close relationship both to the bile pigments and to the blood pigments. 



11. The urine contains also under perfectly normal circumstances reducing 

 substances and proteids, though in very small quantities. 



Besides uric acid and creatinin, the reducing substances are dextrose, iso- 

 maltose (?), animal gum, and conjugated compounds of glycuronic acid (page 

 24 



