380 Chittenden and Painter— Casein and its 
which appeared in every digestion in greater or less quantity, was 
apparently wholly insolubie in fresh portions of gastric juice and 
was similar in its reactions to the like-body previously described by 
Lubavin.* | When fresh, it appeared as a more or less jelly-like 
mass, much like starch paste. It was readily soluble in dilute alkalies 
and precipitated by neutralization, but insoluble in excess of acid. 
It was precipitated from its solution in dilute sodium hydroxide by 
addition of salt in substance. This body we did not attempt to 
study further, but hope to do so later. 
The filtrate from the undigested residue, when cold, was not per- 
fectly clear but became so on the application of a gentle heat. On 
boiling the solution, a very slight precipitate was formed. The addi- 
tion of acids, hydrochloric, nitric or acetic, either concentrated or 
dilute, caused a heavy white precipitate, not wholly soluble in excess 
of acid, even of concentrated hydrochloric. The precipitate was 
likewise more or less permanent when warmed or even boiled with 
the acid. In the filtrate from the precipitate produced by acetic 
acid, the addition of potassium ferrocyanide gave no precipitate. 
The precipitate produced by acids was readily soluble in dilute 
alkalies. On addition of nitric acid, of any strength, and the appli- 
cation of heat even to boiling, the mixture turned first rose color then 
reddish, and as the boiling was continued the color deepened and 
finally became brownish red. The change from rose color to brown 
also takes place in the cold. With concentrated nitric acid the color 
is nearer the yellow of the xanthoprotein reaction, but still shows 
plainly the brown or reddish tinge. 
For separation of the individual caseoses, the entire solution with- 
out being concentrated, was saturated with sodium chloride, by 
which an exceedingly heavy precipitate, more or less curdy, was 
obtained, which was finally filtered off and washed with saturated 
salt solution. The washing was made more thorough by grinding 
the mass with the salt solution in a mortar. This precipitate, by 
analogy, would naturally be composed mainly of a body correspond- 
ing to protoalbumose with possibly something corresponding to hete- 
roalbumose. The precipitate was washed thoroughly with saturated 
salt solution, dissolved in water, filtered, and again precipitated by 
saturation of the fluid with sodium chloride. All of the substance, 
however, was not reprecipitated; quite a little remained in the salt- 
* Ueber die Kiinstliche Pepsin-Verdauung des caseins, ete., Hoppe-Seyler’s Med. 
Chemische Untersuchungen, p. 467. 
