P. A. Levene : POL 
OH. ~ 
O—=P — C;H;0, . C;H,N;O 
OH” 
OH. 
O=—-P a C,;H;0, . C,H,N;O 
OH 
OH, 
OP = C.H.0,. CHING 
OH” 
—3H,0 
OH. 
O=P — C;H,0O, . C;H4N; 
OH” 
* Bottomley has recently (Proc. Roy. Soc., B, 1917, xc, 39) criticized 
the view expressed by Levene and Medigreceanu (J. Biol. Chem., 1911, 
ix, 375, 389) that the first phase in the enzymatic cleavage of nucleic acid 
consisted in the dissolution of the union between individual mononucleo- 
tides; Bottomley modified the theory, accepting that the first: phase of 
decomposition of nucleic acid is limited to its cleavage into two dinucleo- 
tides. This hypothesis may eventually prove correct; however, the evi- 
dence furnished by Bottomley is unsatisfactory. The author made no 
attempt to fractionate his crude material. For the present the conclu- 
sion of Bottomley seems to us unsustained by facts. 
EXPERIMENTAL. 
The condition of hydrolysis and the method of preparation of 
the mixed pyrimidine nucleotides were the same as previously 
described. Care was taken to keep the temperature of the oil 
bath during the hydrolysis at 100°C. 
The crude silver salts were suspended in water and freed from 
silver by means of hydrogen sulfide. The filtrate from silver sul- 
fide was freed from hydrogen sulfide by aeration, then rendered 
alkaline by means of a solution of barium hydroxide in order to 
remove the phosphoric acid. The filtrate was then neutralized 
and concentrated at diminished pressure and at 50°C. From the 
eoncentrated solution the barium was removed quantitatively 
and to the filtrate brucine in methyl] alcoholic solution was added 
until the originally acid solution turned slightly alkaline to litmus. 
On standing, a crystalline deposit of the nucleotides formed. 
The separation of the two nucleotides was brought about by 
recrystallization from 35 per cent ethyl alcohol. After eight 
recrystallizations the brucine salt of a pure uridinenucleotide was 
