STONE, OR GRAVEL. 95 



ent animals by the salts or other constituents found dissolved in the 

 healthy urine, and by the additional constituents M^hich may be 

 thrown off in solution in the urine in disease. In this connection it is 

 important to observe the following analysis of the horse's urine in 

 health : 



Water • 918. 5 



Urea 13.4 



Uric acid and urates "_ . 1 



Hippuric acid 2(>. 4 



Lactic acid and lactates 1.2 



Mucus and organic matter 22.0 



Sulphates (alkaline) 1.2 



Phosphates (lime and soda) .2 



Chlorides (sodium) 1.0 



Carbonates (potash, magnesia, lime) IG. 



1000. 



The carbonate of lime, which is present in large amount in the urine 

 of horses fed on green fodder, is j)ractically insoluble, and therefore 

 forms in the passages after secretion, and its microscopic rounded 

 crystals give the urine of such horses a milky whiteness. It is this 

 material which constitutes the soft, white, pultaceous mass that some- 

 times fills the bladder to repletion and requires to be washed out. In 

 hay-fed horses carbonates are still abundant, while in those mainly 

 grain-fed they are replaced by hippurates and phosphates — the prod- 

 ucts of the wear of tissues — the carbonates being the result of oxida- 

 tion of the vegetable acids in the food. Carbonate of lime, therefore, 

 is a very common constituent of urinary calculi in herbivora, and in 

 many cases is the most abundant constituent. 



Oxalate of lime, like carbonate of lime, is derived from the burning 

 up of the carbonaceous matter of the food in the system, one imj^or- 

 tant factor being the less perfect oxidation of the carbon. Indeed, 

 Fiistenberg and Schmidt have demonstrated on man, horse, ox, and 

 rabbit that, under the full j^lay of the breathing (oxidizing) forces, 

 oxalic acid, like other organic acids, is resolved into carbonic acid. 

 In keeping with this is the observation of liehmann, that in all cases 

 in Avhich man suffered from interference with the breathing oxalate 

 of lime appeared in the urine. An excess of oxalate of lime in the 

 urine may, however, claim a different origin. Uric and hippuric 

 acids are found in the urine of camivora and herbivora, respectively, 

 as the result of the healthy wear (disassimilation) of nitrogenous tis- 

 sues. But if these products are fully oxidized, they are thrown out 

 in the form of the more soluble urea rather than as these acids. 

 Wlien uric acid out of the body is treated with peroxide of lead it is 

 resolved into urea, allantoin, and oxalic acid, and Wrehler and Frer- 

 richs found that the administration of uric acid not only increased 



