298 LECTURE XIII. 



Two other alloxuric bases, the so-called episarkine * and epiguanine, 2 have 

 also been isolated from urine. The latter is 7-methylguanine: 



C . N . CH 3 



N_C_N> H 



Epiguanine 



We must now attempt to answer the question as to what becomes of the 

 remaining constituents of the nucleic acids. We are especially interested 

 in the fate of the three pyrimidines, uracil, thy mine, and cytosine. We 

 should expect them to be related in some way to the formation of uric acid, 

 although H. Steudel, 3 on feeding pyrimidine derivatives to dogs, could not 

 succeed in transforming them into purine compounds. We know nothing 

 else that is definite concerning the behavior of the pyrimidine bases in 

 animal economy. 



As regards the phosphoric acid which is obtained by the cleavage of 

 nucleic acid, we can only surmise what its relations are in metabolism. 

 Possibly it is utilized in the formation of lecithin. 



If we sum up all we know about the breaking down of the nucleoproteids, 

 and especially of the nucleic acids, we see that there are large gaps in 

 our knowledge. It is not yet perfectly clear to us how the nucleo- 

 proteids in the cells themselves participate in metabolism, nor the 

 function of the nucleus in cell-metabolism. Although the study of the 

 uric acid formation has given to us a fairly clear picture of the transforma- 

 tion of purine bases, on the other hand it has not been found possible from 

 this knowledge to shed much light into the obscurity enveloping the 

 metabolic disturbances which occur in gout and uric acid diathesis. We 

 can indeed imagine that in these diseases either the production of uric 

 acid is increased for some reason, or that there is not so much decomposi- 

 tion of this acid as takes place normally. Now uric acid is very difficultly 

 soluble in water, and its occurrence in certain tissues especially in 

 cartilage is to be traced to this fact. His 4 found that one part dissolved 

 in 39,000 of water at 18 C. We shall study these relations at another 

 place, and will here merely mention the fact that of the four hydrogen 



1 Balke: Zur Kenntnis der Xanthinkorper, Inaug. Diss. Leipzig, 1893. Georg Salo- 

 mon: Z. physiol. Chem. 18, 207 (1894). 



2 M. Kriiger: loc. cit. Arch. Anat. Physiol. 1894, 553; Z. physiol. Chem. 24, 364 (1898); 

 26, 389 (1898-99). 



3 Z. physiol. Chem. 32, 285 (1901). 



4 Verh. xvii, Kong. Med. p. 315 (1899); Deut. Arch. klin. Med. 67, 81 (1900);Verh. 

 xviii, Kong. Med. 425 (1900) and Zent. Stoffwechsel-und Verdauungskrankheiten, 1, 

 61 (1900); 3, 434 (1901); His and Paul: Z. physiol. Chem. 31, 64 (1900). 



