COMPOSITION OF THE URINE. 



421 



into the jugular vein of a dog a solution containing about twenty-three grains of urate of 

 ammonia. In the urine, taken a short time after, there was no deposit of uric acid but 

 there appeared numerous crystals of oxalate of lime. The same result followed in the 

 human subject, on the administration of sixty-seven grains of urate of ammonia by the 

 mouth. These questions have more of a pathological than a physiological interest ; for 

 the quantity of oxalate of lime in the normal urine is insignificant, and this salt does not 

 seem to be connected with any of the well-known processes of disassimilation. 



Xanthine, Hypoxanthine, Leucine, Tyrosine, and Taurine. Traces of xanthine have 

 been found in the normal human urine, but its proportion has not been estimated, and 

 we are as yet but imperfectly acquainted with its physiological relations. Under patho- 



FIG. 126. Crystals of tyros in e. (Funke.) 



FIG. 121. Crystals oftaurine. (Funke.) 



logical conditions, it occasionally exists in sufficient quantity to form urinary calculi. It 

 has been found in the liver, spleen, thymus, pancreas, muscles, and brain. It is in- 

 soluble in water but is soluble in both acid and alkaline fluids. Hypoxan thine has never 

 been found in normal urine, although it exists in the muscles, liver, spleen, and thymus. 

 Leucine exists in the pancreas, salivary glands, thyroid, thymus, suprarenal capsules, 

 lymphatic glands, liver, lungs, kidneys, and in the gray substance of the brain. It has 

 never been detected in the normal urine. The same remarks apply to tyrosine (although 

 it is not so extensively distributed in the economy), to taurine and cystine. The last two, 

 however, contain sulphur, and they may have peculiar physiological and pathological 

 relations that we do not at present understand. 



These various substances are mentioned, although some of them have not been demon- 

 strated in the normal urine, for the reason that there is evidently much to be learned 

 with regard to the various products of disassimilation as they are represented by the 

 composition of the urine. While some of these may not be actual proximate principles, 

 but substances produced by the processes employed for their extraction, some, which 

 have thus far been discovered only under pathological conditions, may yet be found in 

 health, and they represent, perhaps, important physiological acts. 



Fatty Matters. Fat and fatty acids are said to exist in the normal urine in certain 

 quantity. Their proportion, however, is small, and the mere fact of their presence, 

 only, is of physiological interest. 



Inorganic Constituents of the Urine. 



It is by the kidneys that the greatest quantity and variety of inorganic principles are 

 discharged from the organism ; and it is probable that even now we are not acquainted 



