New York AGRICULTURAL EXPERIMENT STATION. 217 
ripening process. The more complete our knowledge is in re- 
spect to the various individual compounds formed in cheese- 
ripening, the better can we understand the causes that produce, 
and the conditions that control, the process. Whether or not 
cheese-ripening is in part, or in whole, a biological process, our 
knowledge of the details of the process must depend very largely 
upon our knowledge of the specific chemical compounds result- 
ining from such action. 
More or less work of a desultory character has been done in 
this field. Special difficulties are met in the isolation and study 
of the individual proteolytic compounds found in cheese, owing 
to a lack of knowledge regarding the chemical constitution of 
many of them and also to the minute quantities commonly avail- 
able. Then, too, the same compounds are present or absent 
according to the conditions of ripening, even in cheese of the 
same variety. In different kinds of cheese, there is still greater 
variation. Thus far, we have confined our attention to the study 
of American cheddar cheese, the type most commonly made in 
this country. 
The presence of ammonia was early noticed in cheese. In 1818 
Proust! discovered in old cheese leucine, which he called “ case- 
ous oxide.” In 1880 Siber? found tyrosine in a sample of 
rocquefort cheese. In 1882 Weidmann*® undertook an investiga- 
tion of the chemical compounds of emmenthaler cheese more 
thorough than had been previously attempted. He was the 
first to call attention to a product soluble in hot alcohol, called 
by him “ caseo-glutin,” which we have recently shown to be un- 
saturated paracasein lactate. Rése and Schulze® in 1885 were 
the first to mention the presence of nuclein in cheese, though 
their work was largely qualitative. In 1887 Benecke and 
Schulze® added to the list of nitrogen compounds previously 
found in emmenthaler cheese phenylamidopropionic acid. Re- 
cently Winterstein and Thény’ have reported in emmenthaler 
1Annal. de Chim. et de Phys., [2] 10: 40 (1818). 
2Jour. f. Prak. Chem., N. F., 21: 213 (1880). 
3..andw. Jahrb., 11: 587 (1882). 
4N. Y. Agr. Exp. Sta. Bul. No. 214 (1902). 
5Landw. Versuchst., 31: 115 (1885). 
8Landw. Jahrb., 16: 317 (1887). 
7Zeit. f. Physiol. Chem., 36: 28 (1902), 
