XANTHIXE. 209 



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. 1 

 These questions have more of a pathological than a physio- 

 logical interest ; for the quantity of oxalate of lime in the 

 normal urine is insignificant, and this salt does not repre- 

 sent any of the well-known processes of disassimilation; 



Xanthine (C 10 H 6 !N" 4 O 4 ). Traces of this substance 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 pathologi- 

 cal 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 insoluble in wa- 

 ter, but is soluble in both acid and alkaline fluids. Hypo- 

 xanthine (C 10 H 4 N" 4 O 2 ) has never been found in normal urine, 

 though it exists in the muscles, liver, spleen, and thymus. 

 Leucine (C 12 H, a N" a O 4 ) exists in the pancreas, salivary glands, 

 thyroid, thymus, suprarenal capsules, lymphatic glands, 

 liver, lungs, kidney, and gray substance of the brain. It has 

 never been detected in the normal urine. The same remarks 

 apply to tyrosine (C 18 H n NO 6 ), though it is not go extensively 

 distributed in the economy, taurine (C 4 H 7 ]N~O 6 S 3 ), and cys- 

 tine (C 6 H 6 N 4 O 4 S 2 ). The last two, however, contain sulphur, 

 and may have peculiar physiological and pathological rela- 

 tions that we do not at present understand. 



These various substances are mentioned, though some of 

 them have not been demonstrated 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 



1 WOEHLER TTND FRERiCHS, Ueber die Verdnderungen, welche namentUch or- 

 ganische Stoffe lei ihren Uebergange in den Horn erleiden. Journal fur 

 tische Chimie, Leipzig, 1848, Bd. xliv.,S. 65. 

 14 



