XANTHIN. 389 



only in extremely minute quantities. Thus, from 10,000 liters of 

 urine, Kriiger and Salomon' obtained 10.11 g. of xanthin, 22.35 g. 

 of heteroxanthin, 31.29 g. of 1-methyl xanthin, 15.31 g. of para- 

 xanthin, 8.50 g. of hypoxanthin, 3.54 g. of adenin and 3.40 g. of 

 epiguanin. It is evident from this that xanthin and its methyl 

 derivatives make up the greater part of the purin bases found in the 

 urine. Hitherto these urinary bases have been considered as meta- 

 bolic products of the nuclein of the tissues but recent investigations 

 have demonstrated that there is another and indeed principal source 

 for xanthin and its derivatives. It is now known that caffein and 

 theobromin undergo cleavage in the body and yield the less methyl- 

 ated xanthins. With the fact in mind that a large part of the purin 

 bases in the urine are not derived from the nuclein of the tissues but 

 owe their origin to more complex bases in the food it is evident that 

 the determination of the ratio of the nitrogen of uric acid to that of 

 the purin bases is no criterion of cellular metabolism unless the 

 presence of these bases in the food is first eliminated. 



During the use of sulphur baths, or after the thorough applica- 

 tion of sulphur salves, the quantity of xanthin in the urine is said to 

 be considerably increased. It is likewise more abundant in the 

 urine of leukemic patients, for the reasons already given on p. 348. 

 In small amounts of leukemic urine (two cases) Salomon, however, 

 was not able to detect it by means of the sodium reaction. It was 

 found in one out of four pneumonic urines ; and in two out of ten 

 normal urines from which at times it may be wholly absent. 

 Baginsky holds that the amount of xanthin normally 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 xanthin, but other 

 observers are inclined to regard the crystals as those of hypo- 

 xanthin. Vaughan has reported the presence of xanthin in deposits 

 from the urine of patients with enlarged spleen. 



Xanthin, like the preceding three bases, is widely distributed in 

 animal tissues and in plants. In muscle and in the pancreas it was 

 first detected by Scherer (1859) and since then it has been obtained, 

 though often in mere traces, from all nucleated tissues. Thus, ac- 

 cording to Schindler, in the thymus gland and in the spermatozoa of 

 the carp there are but very small amounts, if any, of xanthin, 

 whereas the sarkin bases, especially adenin, are present in abundance. 

 This observation has been confirmed by Inoko. The xanthin bases 

 (xanthin and guanin) are obtained in variable but greater amount 

 than the sarkin bases (adenin and hypoxanthin) from the pancreas 

 and from spermatozoa of the bull, boar and salmon. The bases rich 

 in oxygen, as hypoxanthin and xanthin, are more abundant (2 to 1) 

 than those rich in nitrogen (adenin and guanin, Inoko). Inoko 

 ^Zeits./. phygioL Chem., 26, 367, 1898. 



