368 CHEMISTRY OF THE LEVCOMAINS. 



Eecent advances in biological chemistry have shown that the 

 undeveloped eggs of various insects and birds yield much less xan- 

 thin bodies (hypoxanthin, xanthin, etc.) on treatment with dilute 

 acid than do the partially developed eggs (Tichomiroff, Kossel). 

 This is dependent upon the remarkable fact observed by Kossel that 

 the nuclein of undeveloped chicken eggs differs from the nuclein of 

 cell nuclei and resembles that obtained from milk. For, while the 

 nuclein from the cell nuclei decomposes into adenin, guanin, hypo- 

 xanthin, etc., that from undeveloped eggs and from milk yields no 

 nitrogenous bases on treatment with acids. But as the egg develops, 

 i. e., the nucleated cells increase in number, this latter nuclein is 

 gradually converted or gives way to the ordinary cell nuclein, and 

 hence it is that the chick embryo yields guanin, hypoxanthin, and 

 possibly adenin. 



Unquestionably, the presence of hypoxanthin, etc., in developing 

 cells is due to the presence of the nuclein molecule from which it is 

 readily split off. In muscle, however, hypoxanthin and xanthin 

 appear to exist preformed, and bear no relation to nuclein, since they 

 are in the free condition, and can be extracted from the tissue by 

 water. This condition is analogous to that observed in plants, such 

 as tea, and in sprouts and is undoubtedly due to an enzyme action 

 on nuclein (p. 348). 



According to the observations of Salomon and Chittenden, hypo- 

 xanthin is formed by the digestion of blood fibrin with gastric juice, 

 pancreatic juice, or on heating with water or dilute acids. Egg 

 albumin under the same conditions does not yield any hypoxanthin, 

 except when treated with pancreatic juice. These observations re- 

 quire repetition, inasmuch as the fibrin used undoubtedly contained 

 nuclein, which, as we now know, readily decomposes under those 

 conditions into its characteristic nitrogenous bases. 



Hypoxanthin can be readily obtained from a number of closely 

 related substances. Thus, carnin, by the action of oxidizing agents, 

 is converted into hypoxanthin. For this reason Weidel and Schiit- 

 zenberger regarded hypoxanthin as derived from carnin and this 

 view may be in part correct for it is not improbable but that carnin 

 which is a purin base exists at times in the nuclein molecule or is 

 formed during the metabolism of the purin radical. 



Again, it can be obtained from adenin (p. 353) by the action of 

 nitrous acid. The relation that hypoxanthin bears to uric acid 

 had not been definitely established until Kriiger showed that 

 the constitution of hypoxanthin was closely connected with that 

 of uric acid and the xanthin compounds. Streckler's belief that 

 hypoxanthin by oxidation yields xanthin, and that uric acid 

 by reduction with sodium amalgam yields first xanthin and then 

 hypoxanthin, was not confirmed by Kossel or by Fischer. The 

 reported change of uric acid into xanthin and hypoxanthin by 



