17v Reporr oF THE CuemicAL DEPARTMENT OF THE 
were present only in small numbers. Even when large numbers 
were added to milk before making it into cheese, these bacteria 
ceased to grow almost as soon as the curd was put into the 
press and rapidly disappeared in the cheese. 
It was found that from the time cheese was made until fully 
ripened there were present few besides lactic acid bacteria, so 
called because they curdle milk by production of acid without 
Subsequent digestion of the casein. From these results von 
Freudenreich was led to question the connection between 
enzyme-forming bacteria and ripening process. He made numer- 
ous attempts to produce cheese with the addition of cultures 
of enzyme-forming bacteria, which uniformly resulted in a 
product of poorer flavor, according to his opinion. He then 
became the champion of the theory that lactic acid bacteria are 
the principal, if not the only, cause of cheese ripening.® 
The chief objection to this theory is the fact that no one has 
yet been able to demonstrate the production of an enzyme on 
the part of lactic acid bacteria. Without such aid it is difficult 
to understand how a becterium is to attack an insoluble sub- 
stance such as the coagulated casein in cheese. 
Von Freudenreich’? added chalk to milk cultures of these lactie 
acid bacteria for the purpose of preventing the accumulation of 
acid and of simulating in this respect the conditions found in 
cheese. He was thus able to demonstrate the ability of these 
organisms to increase materially the amount of soluble nitrogen. 
However, Chodat and Hoffman-Bang* have pointed out that 
this is not equivalent to attacking the casein after it has been 
coagulated by rennet. They maintain that lactic acid becteria 
are unable to attack coagulated casein, even when sugar is not 
present. 
In a later publication Jensen,? without bringing forward 
adequate experimental evidence, has suggested that lactic acid 
bacteria are able to elaborate an enzyme. 
®y. Freudenreich. Cent. f. Bak., II Abt., 1:384 (1895). 
7y, Freudenreich. Cent. f. Bak., II Abt., 3:231 (1897). 
®Chodat and Hoffman-Bang. Ann. Inst. Pasteur, 15:36 (1901), 
*Jensen. Landw. Jahrb. d. Schweiz., 14:197 (1900). 
