New York AGRricuttcuRaL ExpsrRiMENtT STATION. 17i 
In 1897 Babcock & Russell! announced that the milk of all 
mammals contains, in addition to the previously known sub- 
stances, galactase, a tryptic-like ferment capable of producing 
digestion of casein, and they suggested that this substance 
might play a considerable role in cheese ripening. The correct- 
ness of their statements regarding the existence of this sub- 
stance has been substantiated by Storch,“ von Freudenreich” 
and Jensen.*8 
In 1901 Babcock, Russell and Vivian and Jensen almost 
simultaneously called attention to the ability of pepsin, con- 
tained in rennet solution, to render casein soluble, and they 
presented experimental evidence to establish this point. 
Thus, we see that cheese, as ordinarily manufactured, contains 
enzymes derived from three different sources, (1) bacteria, (2) 
milk glands of cows and (38) rennet. 
Enzymes, in acting upon casein, cause its decomposition and 
probably produce compounds that furnish some of the cheese 
flavors. While we appreciate as highly important, from a 
practical standpoint, the study of cheese flavors, we have 
devoted our time chiefly to a study of enzyme action upon cheese- 
casein. It seems that this constitutes so fundamental a prob- 
lem in cheese ripening that it should be first studied, and more- 
over its solution will doubtless go far toward solving the 
probiem of flavors. 
II. METHODS OF CHEMICAL ANALYSIS USED. 
In a later bulletin the methods of chemical analysis used in 
determining the amounts of nitrogen present in different forms 
in cheese wili be presented and discussed in full detail. In this 
connection it seems sufficient to present only a brief outline of 
such methods. 
*Babcock and Russell Ann. Rept. Wis. Exp. Sta. 14:161 (1897). 
“Storch. 40 Rept. Copenhagen Exp. Sta. (Denmark). 
vy. Freudenreich. Cent. f. Bak., II Abt., 5:241 (1899). 
®Jensen. See footnote 9. 
* Babcock, Russell and Vivian. Ann. Rept. Wis. Exp. Sta. 17:102 (1900), 
also Cent. f. Bak., II Abt., 6:817 (1900). 
Jensen. Landw. Jahrb. d. Schweiz., 14:197 (1900), also Cent. f. Bak., 
“II Abt., 6:734 (1900). 
