CHEMISTRY OF THE LEUCOM AINES. 313 



acidulated solution of guanine, when a light, crystalline 



precipitate forms. Under the microscope it appears in 



pencil-shaped, fern-like tufts of fine, orange-yellow needles. 



Physiologically guanine like uric acid is inert (Filehnb). 



Xanthine, CjH^N^Oj, is also veiy widely distributed in 

 the organism, and has been met with in almost all the 

 tissues and liquids of the animal economy. Together with 

 hypoxanthine, guanine, and possibly adenine, it occurs in 

 many plants, among which may be mentioned lupine, 

 sethalium, sprouts of malt, tea-leaves (Baginsky), auto- 

 digestion of yeast, gourd seeds, soja beans, etc. It was 

 first discovered by Marcet (1819) in a urinary calculus, 

 and since then has been frequently found as the only or 

 chief constituent of many calculi. Unger and Phipson 

 have extracted it from guano, while Salomon has shown 

 it to be one of the products formed in the pancreatic diges- 

 tion of fibrin. Schutzenbbrqer found it together with 

 camine and hypoxanthine in the liquors from yeast. It is 

 a normal constituent of the urine, but is present only in 

 extremely minute quantities. During the use of sulphur- 

 baths, or after the thorough application of sulphur salves, 

 the quantity of xanthine in the urine is considerably in- 

 creased. It is likewise more abundant in the urine of leuco- 

 cythsemic patients, for the reasons already given on page 

 283. Baginski holds that the amount of xanthine nor- 

 mally present in the urine may be increased tenfold in the 

 case of acute nephritis. Bence Jones observed in the 

 urine of a child sick with renal colic, a deposit of crystals 

 which he considered to be xanthine, but other observers 

 are inclined to regard the crystals as those of hypo- 

 xanthine. Vaughan has reported the presence of xan- 

 thine in deposits from the urine of patients with enlarged 

 spleen. 



Xanthine may be prepared synthetically in several ways. 

 Thus, it may be obtained by the reduction of uric acid by 

 means of sodium amalgam, according to the equation : 



TJeio Acid. Xanthine, 



