THE NUCLEINIC ACIDS. 75 



however, that these acids actually represent mixtures of different 

 nucleinic acids, and Kossel expresses the opinion that in reality 

 only four true nucleinic acids exist, viz., adenylic acid, guanylic 

 acid, sarcylic (hypoxanthylic) acid, and xanthylic,acid. He further 

 believes that only one nucleinic base is represented in each one of 

 these acids, viz., adenin, guanin, hypoxanthin, and xanthin. In 

 accordance with this supposition, the spermanucleinic acid of the 

 ox would contain three acids, as on decomposition it yields xan- 

 thin, hypoxanthin, and adenin. Thymonucleinic acid, from which 

 only adenin and guanin have been isolated, would similarly repre- 

 sent a mixture of adenylic acid and guanylic acid, etc. This 

 assumption of Kossel, however, has not proved correct, for we 

 now know that his adenylic acid, for example, contains not only 

 adenin, but also guanin and a third basic substance which has been 

 termed cytosin Bang, on the other hand, has shown that a nucleinic 

 acid can be isolated from the pancreas which contains only one 

 nucleinic base, guanin, and which would thus correspond to KossePs 

 hypothetical guanylic acid. Then, again, it appears that the so-called 

 mosinic acid, which has been found in muscle-tissue, contains only 

 hypoxanthin. But we see nevertheless that more than one of the 

 nucleinic bases may occur in the molecule of one nucleinic acid. 



All nucleinic acids contain carbon, hydrogen, nitrogen, oxygen, 

 and a large percentage of phosphorus, of which* indeed one part is 

 usually found for every three parts of nitrogen. Sulphur is not 

 present. Of the form in which the phosphorus exists in the nucle- 

 inic acid molecule but little is known. The assumption that the 

 true nucleins represent compounds of albumins Avith metaphos- 

 phoric acid, to which metaphosphates of xanthin and guanin are 

 admixed, is no longer tenable. According to Kossel, the nucleinic 

 acids possess a radicle which contains a number of phosphorus 

 atoms united to each other after the manner of the polymetaphos- 

 phoric acids, and the evidence is now conclusive that the nucleinic 

 bases are present in the nucleinic acid radicles as organic com- 

 pounds. Of special interest, further, is the fact that some of the 

 nucleinic acids contain a carbohydrate group. From yeast-nucleinic 

 acid Kossel was thus able to obtain a hexose as well as a pentose. 

 In guanylic acid a pentose is also apparently present, and from the 

 spermanucleinic acid of the sturgeon, as also from thymonucleinic 

 acid, Isevulinic acid can be obtained. 



As regards the structural composition of the individual nucleinic 

 acids, our knowledge is very incomplete. The general formulae of 

 the more important members of the group are here given : 



Spermanucleinic acid of the salmon C 40 H 54 N, 4 O 17 .2P 2 O 5 



Yeast-nucleinic acid C 40 H 5 <jN, fi O 2 2.2P 2 O 5 



Thymonucleinic acid C 25 H 36 N 9 O. 20 P3 



Guanylic acid ( '22^34^ icPu-f-Ai 



Inosinic acid Cj H 13 N 4 O 8 P 



On decomposition the primary nucleinic acids give rise to the 



