192 REPORT OF THE CHEMIST OF THE 
this work has assumed that paracasein formed the primary point 
of attack or starting point in these changes. Our results, pre- 
sented in the foregoing pages, suggest that unsaturated para- 
casein lactate, and not paracasein, is the real material with 
which the process of cheese-ripening commences. It is not our 
purpose, at this time, to go into the subject in more than a pre- 
liminary way. In connection with Table II, p. 174, attention has 
been called to the fact that the amount of water-soluble nitrogen 
in cheese, which is a general measure of the extent of cheese- 
ripening, increases at the same time that the unsaturated para- 
casein lactate decreases, and probably at the expense of the latter 
compound. 
The belief that the proteolytic changes of cheese-ripening actu- 
ally start with the unsaturated paracasein lactate receives con- 
firmatory evidence from the fact that, in the absence of un- 
saturated paracasein lactate in cheese, we have very incompiete 
proteolytic change. In order to establish beyond question the 
specific relation of unsaturated paracasein lactate to the pro- 
teolytic changes of cheese-ripening, we have under way numerous 
experiments in which preparations of pure unsaturated para- 
casein lactate are being subjected to the action of a variety of 
agencies, such as different enzymes and organisms that have 
been commonly associated with the different theories of cheese- 
ripening. 
Some results, already secured, appear to indicate that the first 
proteolytic changes in cheese-ripening are the result of peptic 
digestion of unsaturated paracasein lactate. In cheese, pepsin 
appears to act, not to any marked extent upon the proteid para- 
casein, but only upon its unsaturated compounds with acids. 
Hence, the function of an acid in cheese-making is the production 
of an unsaturated compound of paracasein with acid. This sug- 
gests that something of the same kind of action may be found 
to be true in the case of gastric digestion. It is well established 
that pepsin acts upon proteids in the stomach only in the presence 
of dilute acid. The function of the hydrochloric acid of the gas- 
tric juice, like lactic acid in cheese, may be the formation of com- 
pounds with proteids; in other words, it may be found that pep- 
