252 THE URINE. 



washed into a beaker, after opening the filter, using about 100 c.c. 

 of water. Fifteen c.c. of concentrated sulphuric acid are then added 

 and the solution is titrated at once with a one-twentieth normal solu- 

 tion of potassium permanganate. Toward the end of the titration 

 Folin suggests to add the permanganate in portions of two drops at 

 a time, until i\\e first trace of rose is apparent throughout the entire 

 fluid. Each cubic centimeter of the reagent corresponds to 0.00375 

 gramme of uric acid. A final correction of 0.003 gramme for every 

 100 c.c. of urine employed is necessary, owing to the slight degree 

 to which ammonium urate is soluble. 



The Xanthin Bases. 



The xanthin bases which have been found in the urine of man 

 are xanthin, hypoxanthin, guanin, carnin, paraxanthin, heteroxan- 

 thin, episarcin, and under certain pathological conditions adenin. 

 Their amount is always small, and normally constitutes about 10 

 per cent, of the quantity of uric acid, viz., from 0.02 to 0.06 

 gramme. Of this amount 0.02 to 0.03 gramme is represented by 

 xanthin. Hypoxanthin and guanin probably stand next in order, 

 while paraxanthin and heteroxanthin are found only in traces. 

 From 10,000 liters of urine Kriiger and Salomon obtained only 7.5 

 grammes of the latter. 



Origin. It has been shown that the xanthin bases are derived 

 from the nucleins, and are probably formed in all tissues of the 

 body (endogenous form). In addition a certain amount is intro- 

 duced from without (exogenous form). Under normal conditions 

 the greater portion of the xanthin bases is no doubt oxidized to 

 uric acid, but a variable fraction escapes as such. To a certain 

 extent the oxidation to uric acid occurs in the liver, but, as I have 

 shown, this takes place also in the other organs of the body (notably 

 the muscle tissue), as both xanthin bases and uric acid are obtained 

 in transfusion experiments. At the same time it was noted that the 

 relative amount of the two was largely influenced by the degree of 

 oxygenation of the blood, so that xanthin bases only were obtained 

 if venous blood was used, while both were found when arterial blood 

 was employed. We can thus understand that, as a general rule at 

 least, a certain relation exists in the elimination of uric acid and the 

 xanthin bases. A diminished elimination of the latter is thus quite 

 frequently associated with a corresponding increase of the former, 

 or vice versa, and both may, of course, be increased or diminished 

 together. The most notable increase in their elimination is ob- 

 served in leukaemia, and here adenin also appears in the urine. 



Theobromin (dimethyl-xanthin) and caffein (trimethyl-xanthin) 

 are partly eliminated in the urine as such, and partly appear as a 

 methyl-xanthin which is apparently identical with heteroxanthin. 



Xanthin has once been found in crystalline form in a urinary 

 sediment, and has in several instances been encountered in vesical 

 calculi. 



