Primary Cleavage Products. 391 
present case, the pepsin solution employed was much weaker and the 
pepsin-casein mixture was warmed at 45° C. for several days instead 
of hours. 
750 grams of casein were employed and 4 litres of 0:4 per cent. 
hydrochloric acid, to which was added a reasonable amount of pure 
pepsin solution. About an hour after the addition of the latter the 
mass began to gelatinize, and at the end of 18 hours the whole mix- 
ture was a perfectly stiff jelly. Thereupon, 2 litres more of 0:4 per 
cent. acid were added together with a little pepsin. The mixture was 
then kept at 40-45° C. for three days longer. Quite a large residue 
of undigested matter remained, semi-gelatinous and soluble only in 
alkalies. The mixture was then neutralized and filtered. The 
filtrate contained considerable caseose, as evidenced by the heavy 
precipitate obtained on saturating a portion with sodium chloride. 
In the preceding digestions, the caseoses were separated directly 
from the dilute ‘solutions, without previous concentration, thereby 
avoiding any possible change due to the action of heat. In the pre- 
sent case, however, the perfectly neutral solution was evaporated to 
a small volume and then all of the caseoses were directly precipitated 
by saturating the fluid with ammonium sulphate. The precipitate 
produced was exceedingly gummy, but was washed as thoroughly 
as possible by trituration with a saturated solution of ammonium 
sulphate. The caseoses were then dissolved in water, the solution 
filtered from the small residue of insoluble matter and saturated 
with sodium chloride. The protocaseose so separated was freed from 
heterocaseose, etc. by repeated precipitation and dialysis. 
Carbon and hydrogen were determined in a portion of the dried 
substance (Protocaseose C 1) with the following results: 
I. 05107 gram substance gave 0°3101 gram H.O=6:74 per cent. H and 
0:9386 gram CO.=50°11 per cent C. 
II. 0°4088 gram gave 0:0194 gram ash = 4°80 per cent. 
The ash-free substance would, therefore, contain 52°64 per cent. of 
carbon and 7:08 per cent. of hydrogen. 
In the filtrate from the first salt precipitate, the protocaseose re- 
maining was precipitated by the addition of a little salt-saturated 
acetic acid. The precipitate after being washed was dissolved in a 
little dilute sodium carbonate, the solution neutralized and dialyzed. 
As no heterocaseose separated from the solution, it was concen- 
trated and then precipitated by alcohol. After purification by re- 
solution, dialysis, etc., it was dried at 105° C. in vacuo and analyzed 
with the results shown in the accompanying table (Protocaseose C 2), 
