CHEMISTliV OK THK VKAST CELL NL\'LKU.S. 163 



which he iifterwiinls iiiijuoveil (IX.), Jiml showed (\'llL)thut the 

 Siiiue isalso obbiiuahle from uucleius of different (utiiuml) origin. 

 In the lutMiitiine he isohited (HI.) from yea.st nuclein a second 

 1>ise. xanthin (C^II^X^O.,), t<j which he achled a third, namely 

 guanin ((Vll X-_0) in 1882 (IX.). The occurrence of the hist/- 

 named in yeast ha.snlso been placed beyond doubt by S. Sciiixdler 

 (I.). These three allies of uric aci(i (Cj^H^Nj^Oy) had already 

 been long known to chemists, though not as con.stituents of 

 nucleins. On the other hand, the four additiomil ba.se.s men- 

 tioned below were all new, and were obtiiined for tlie first tinie 

 from tlie nucleins. Adenin (CH.X,) was i.solated bv KossEL 

 {XI.) in 18S5, fir.st from the nuclein of ox pancreas and afterwards 

 from pre.s.sed yeast. This .substjiuce stsiuds in the Siime relation 

 towards hypoxanthin as guanin does to xanthin, not only as far 

 as chemical composition is concerned, but ahso in respect of 

 behaviour during putrefaction caused by certiiin bacteria, which, 

 according to the rese:irches of S. Schin'dleh (I.), degrade guanin 

 to xanthin, and adenin to hypoxanthin. According to A. 

 Bagi.nsky (IV.), the last-named offers the greater i-e.sistance to 

 the influences in question. In 1893 another new base, namely 

 thymin. was brought to our knowledge by A. Kossel and A. 

 Nelm.vn.v (I.). It was first obtained from the nucleic acid 

 i.solated from the thymoid gland of the calf, which acid received 

 the name of adenylic acid on account of its capacity for furnishing 

 udonin. The thvmin molecule (which has the formula CH,.X.,0.,) 

 may be regarded as methyl-dioxy-pyrimidin, in conformity 

 ■with the views of H. Stel"DEL (I.), or as 5-methyl-ui':icyl, in 

 sympathy with those of E. Fischer and (J. Rikder (I.), who 

 were the fiist to prepare it by .synthetic means. The hypothesis 

 i-jii.sed l>y K0.SSEL and Xei.mann (U.) that thymin is also i)re- 

 sent in the molecular complex of the nucleic acid of yesist, 

 has not been confirmed, though, according to A. Ascoli (III.), 

 the parent sub.stjince of thymin, namely uracyl (C^H^N.O.,) 

 is found therein. It may also be remaiked bv the way 

 that the fourth of the new nuclein bases, cytosin, has so far 

 only been found as a constituent of nucleic acitls of animal 

 •origin. In the crvstiilline stiite this substance has the formula 

 C.,,H.,oN,,0,. 5H.,6. 



Apart from the la.st-named, which has not yet been suffi- 

 ciently investigated, the nuclein bases mentioned may be 

 dassifieil into two groups in accordance with their constitu- 

 tion Adenin, .xanthin, hypoxanthin, and guanin are deriveil 

 from the atomic complex to which Emil Fiscuer (I.) gave the 

 name Piirin : — 



