136 SCIENCE PROGRESS. 



cytosin, which Kossel * has obtained from thymus-nucleic 

 acid in conjunction with adenin and guanin when the 

 acid is boiled for twenty minutes in water. This base has 

 a formula C 2I H 30 N l6 4 5 aq, and is precipitated by phospho- 

 tungstic acid, and forms crystalline salts with sulphuric and 

 hydrochloric acids, and with platinum chloride or gold 

 chloride. It is precipitated in the form of a silver com- 

 pound by an ammoniacal solution of silver oxide. It was 

 obtained to the amount of 2 per cent, of the nucleic acid 

 from which it was derived. 



We thus see that with regard to the nuclein bases they 

 yield, the nucleic acids prepared from different organs have 

 different constitutions, and Kossel suggests that for each base 

 there is a corresponding nucleic acid, there being at least 

 four of these. For these acids he suo-crests the names 

 xanthylic, adenylic, etc. We cannot, however, as yet con- 

 sider this as proven, the alternative that a nucleic acid may 

 have one or more of different basic molecules within it 

 being quite as probable, and, moreover, it explains the facts 

 just as well as the other supposition. It is probable too 

 that far greater differences lie in the other parts of the 

 nucleic acid molecule than the variation in the alloxuric 

 base with which it is combined. A further point of some 

 importance is that though in these nucleic acids we are 

 dealing with a compound of a body of distinct acid pro- 

 perties with a base, yet it is not of the nature of a salt. 

 Kossel and Neumann 2 have shown that if thymus-nucleic 

 acid be boiled in water for about five minutes the acid is 

 split up into the nuclein bases, in this instance adenin to- 

 gether with smaller quantities of guanin and cytosin, and 

 a phosphorous rich acid which they term thyminic acid. 

 Thyminic acid contains no further nuclein base, but if an 

 alloxuric base is added to its solution a thyminate of the base 

 is found. This, however, differs from the original nucleic 

 acid, for if the two substances are treated with barium 

 hydrate and the resulting solutions precipitated by throwing 



1 Kossel : Ber. d. d. chem. Ges., Bd. 27, S. 2215, 1894, and Arch. f. 

 {Anat. u.) Physiol., 1894, S. 551. 



2 Kossel and Neumann: Zeitschr. physiol. Chem., Bd. 22, S. 81, 1896. 



