URINE. 521 



and consists principally of sodium urate, colored by a 

 very small quantity of a red substance, as yet unin- 

 vestigated. In diseases, substances are frequently found 

 in the urine, which it does not contain in a healthy 

 condition. In many varieties of dropsy, and a few 

 other diseases, it contains albumen ; it then becomes 

 turbid on the addition of nitric acid and by heating. 

 In jaundice it contains ingredients of bile; in diabetes, 

 grape-sugar, frequently in very large quantity, and is 

 then secreted to an enormous extent. It is in this con 

 dition fermentable, and afterwards, 011 being subjected 

 to distillation, it yields alcohol. When the origin of 

 the pneurnogastric nerve in the brain is injured, sugar 

 occurs in the urine. Further, lactic acid,lactates, indigo, 

 or, rather, a substance capable of producing indigo 

 (cf. p. 384), leucine, ty rosin, taurine, etc., are occa 

 sionally contained in urine. 



In certain diseased conditions of the body, difficultly 

 soluble ingredients of the urine are deposited even in 

 the urinary canals, and form concretions (gravel and 

 urinary calculi), frequently of great size and hardness, 

 and of very varying composition. Most of them con 

 sist of uric acid with ammonium urate ; others are 

 mixtures of calcium phosphate with magnesium ammo- 

 nio-phosphate ; others consist of calcium-oxalate ; many 

 are formed of alternating layers of all of these sub 

 stances. Calculi consisting of cystine (p. 175) and xan- 

 thine (p. 246) are the most rare. 



Urine is of very varying character according to the 

 class of animals from which it is obtained. That of 

 the higher classes always contains urea in predominant 

 quantities; in that of the lower classes, on the other 

 hand, uric acid is more abundant. The urine of the 

 lion and tiger is so abundantly supplied with urea, 

 that frequently, without previous evaporation, the 

 addition of nitric acid causes the nitric acid compound 

 to crystallize out in laminae. In the urine of dogs 

 there is frequently obtained a peculiar crystallizing 

 acid, kynurenic acid, as yet but little known. The 

 urine of birds and amphibious animals is a white, 

 pulpy mass (after drying, earthy), which consists almost 



44* 



