Art. VII.] Weinzikl, Bactcfia in Cheese. 155 
are unable to say. It is to be noted, however, that the Swiss 
Emmenthaler and the American Cheddar both belong to the 
same general class of firm cheese. That the numbers should be 
high in our analysis of milk and cheese in its early ripening 
stages is not so surprising, when we consider that all the 
mechanical steps in the manufacture of cheese are such as to 
offer the most favorable conditions for development of bacteria. 
The milk is ripened at nearly blood heat and the curd is also 
developed at a comparatively high temperature. 
The most striking fact of our analyses is the overwhelming 
preponderance of the class of germs we have designated as the 
lactic acid bacteria, while the casein digesters are relatively few 
in numbers, and soon disappear from the cheese entirely. This 
practically confirms the conditions found by Von Freudenreich 
in Swiss cheese. The preponderance of acid producing germs 
is readily explained, in that the art of cheese-making consists 
largely in producing those conditions which favor the develop- 
ment of these very germs to the exclusion of others. It is the 
cheese-maker’s constant care to produce sufficient acid to 
make the curd “ string on the hot iron,” and it is these germs 
which change the sugar of the milk into the highly desirable 
lactic acid. Naturally, the question will be asked, what is the 
use of this acid ? 
At first thought, it would seem that the curing of the 
cheese is causally related to this acid or to the acid germs. Von 
Freudenreich,^ in a recent article so concludes. By adding 
chalk to sterilized milk, which was inoculated with a pure cul- 
ture of a lactic germ, the acidity of the milk was neutralized 
and the germ could endure for a much longer time than in cul- 
tures without the addition of this material. It was found that 
under these conditions, which he assumes to be parallel with 
those found in cheese, a certain amount of breaking down of 
the casein took place, but less than occurs in the cheese nor- 
mally. This evidence, though strong, is not conclusive, for 
^ Cent. f. Bakt. 2nd. Abt. Bd. Ill, p. 234. 
