Art. VII.] ' Weinzirl, Bactefia in Cheese. 157 
ing an unknown ferment from milk, was accomplished. They 
demonstrated conclusively that this unorganized ferment is not 
produced by bacterial activity, but is inherent in the milk itself. 
This ferment was found to have the power of changing casein 
into soluble peptones under asceptic conditions. It was further 
found that heat destroyed this ferment and this explained the 
fact why Duclaux was unable to ripen cheese made from steril- 
ized milk, which experiment we had repeated and found to be 
correct. From their experiments they incline to the belief “that 
the ripening of hard cheese, instead of being due solely to bac- 
teria, is caused by the joint action of both organized (bacteria) 
and unorganized ferments (enzymes). The breaking down of 
the casein is undoubtedly due, in larger part, to the action of 
enzymes.” Thus, after half a century the pendulum has .swung 
back to the side of the chemists. However, the new theory 
agrees with that of Ducleaux, in so far that both are based upon 
the action of enzymes; the differe nee being as to their origin. 
The former considered them bacterial, the latter finds them 
to be inherent in the milk. 
However, to explain the cause of the curing phenomenon, 
is not the only nor even the essential part of this paper. There 
still remains to be explained the fact of the enormous numbers 
of these lactic germs and the relatively few germs of the other 
types. That the inert forms should be few or absent is what 
might have been expected. Undoubtedly they gained entrance 
from the air ; but falling in a medium not especially adapted to 
them, they were crowded out or, so to speak, smothered, by 
the growth of the acid forms. The absence of the casein 
digesters is readily explained by the fact that they are inhibited 
by the activity of the lactic acid organisms. If the latter class 
is destroyed as in pasteurization, the digesters, having a free 
field, develop in abundance. 
As to the gas germs, it is a fact that these are, as a rule, 
also moderate producers of acid. That they are correspond- 
ingly more numerous and stand next in number to the purely 
acid forms, is readily understood. But these same gas germs 
are the bane of the cheese-maker, and how he is able to keep 
