THE NUCLEINIC BASES. 77 



the filtrate is treated with an equal volume of alcohol and hydro- 

 chloric acid to the extent of from 3 to 5 pro mille. In this manner 

 impure nucleinic acid is thrown down, which can be further purified 

 by solution in ammoniacal water and further treatment with acetic 

 acid, hydrochloric acid, and alcohol, as just described. 



Thyminic acid differs from the nucleinic acids proper in its ready 

 solubility in cold water, and in the fact that it is not precipitated 

 from its solutions by the mineral acids. Like the nucleinic acids, it 

 gives a precipitate with albumins or primary albumoses (propep- 

 tones) in acetic acid solution, but, in contradistinction to the nucleinic 

 acids, this precipitate is soluble in hydrochloric acid and in solu- 

 tions of many salts. 



Plasminic acid likewise precipitates albumins in acid solution, 

 but, unlike the nucleinic acids, is easily soluble in water ; on treating 

 with ammonia a yellow color develops. Its phosphoric acid radicle 

 is capable of binding iron in such form that it appears like a true 

 organic iron compound. According to Ascoli, the substance contains 

 1 per cent, of iron. It does not give MillonV reaction nor the 

 Liuret reaction, and contains no sulphur. On decomposition with 

 mineral acids by boiling it yields nucleinic bases and phosphoric 

 acid. The substance may be obtained from yeast. 



The question whether the paranucleins contain an acid radicle which 

 is analogous to the nucleinic acids is still undecided. If they occur, 

 such paranucleinic acids, as they would be termed, could, of course, 

 not contain any basic radicle of the character of the nucleinic bases. 

 A few isolated observations seem to show that such acids exist. 

 Altman thus obtained an acid from the yolk of eggs which he re- 

 garded as a nucleinic acid. As the nucleinic bases, however, cannot 

 be obtained from the same source, it follows that the substance in 

 question could not be a true nucleinic acid. Wildenow further 

 speaks of a phosphorus-containing substance, which she was able to 

 obtain from the paranuclein of casein, and which precipitated 

 albumins. Neither of these bodies, however, has as yet been 

 isolated in a form suitable for analysis. Whether KossePs so- 

 called paranucleinic acid, which was later shown to be the same as 

 thymonucleinic acid, is identical with the prosthetic group of the 

 paranucleins, remains to be seen. Its properties certainly are such 

 as would a priori be expected from a true paranucleinic acid. But 

 even if a group of this order were found in some of the paranucleins, 

 its presence in all would not necessarily follow, and it is quite con- 

 ceivable that in others the albumin is directly combined with a phos- 

 phoric acid. 



THE NUCLEINIC BASES. 



The nucleinic bases, which are also spoken of as the xanthin, 

 alloxuric, or purin bases, are found widely distributed both in the 

 animal and the vegetable world. They occur either in the free 

 state or as constitutents of the nucleinic acids and the nucleins. 



