230 Yeast Nucleic Acid. II 
nucleotide. And yet, such a conclusion did not appear entirely — 
compelling, and further attempts at fractionation seemed de- 
sirable. Crystallization of the same crude brucine salts from a 
35 per cent solution of ethyl alcohol was now resorted to. Pass- 
ing the salts through eight recrystallizations, it was possible to 
separate them into two principal fractions. The less soluble 
part had a composition of the salt of uridinephosphoric acid and 
the: more soluble that of cytidinephosphoric acid. Each of these 
could be converted into its barium salt. The barium salt of the 
uridinephosphoric acid precipitated out of a concentrated aqueous 
solution in the form of long needles, aggregated in rosettes re- 
sembling in form those of an osazone. On the other hand, the 
barium salt of the cytidinephosphoric acid appeared under the 
same conditions in the form of microscopic granules. The two 
salts differed in their solubility and in their optical rotation. In 
this communication only the results of the analysis of uridine- 
phosphoric acid will be reported since attempts are still in prog- 
ress to obtain the barium salt of the cytidinephosphoric acid also 
in crystalline form. The purity of the uridinephosphoric acid has 
been proven by the fact that amino nitrogen could not be detected 
on the analysis, either of the barium salt directly, or after pre- 
vious hydrolysis. Nor was it possible to isolate from the product 
of its hydrolysis any other base than uracil. The specific rotation 
of the substance was [a]; = + 3.5°. 
Thus it is evident that the substance previously described as 
pyrimidine dinucleotide was a mixture of two mononucleotides. 
This observation is important inasmuch as it demonstrates con- 
clusively that for the present there is no experimental proof 
for the assumption of a tetra-ribose as the nucleus of yeast 
nucleic acid. This, however, does not exclude the possibility 
that such proof may be furnished in the future. Meanwhile the 
structural formula of yeast nucleic acid, free from all arbitrary 
elements, may be written in the following form. 
