THE HARD CHEESES. IQ9 
ditions, which is responsible for the chemical changes that take 
place in the ripening cheese. This conclusion, however, has not 
been very generally accepted; for while the lactic acid bacteria, 
under these conditions, do produce a certain amount of peptoniza- 
tion of the casein, the action is extremely slow and not very complete; 
and it has not seemed to most students that the phenomenon in 
question is sufficiently explained by this slow action of the lactic acid 
bacteria. 
Flavor Production by Bacteria. Apparently the flavors must 
be due to bacterial action. Cheeses ripened in chloroform vapor, 
which allows the enzymes to act, but prevents bacteria from growing, 
though they ripen, do not develop flavors and these must be due to 
some other cause than enzyme action. That they are the end- 
product of chemical decomposition seems to be extremely probable. 
In many cases they are associated with ammonia; and ammonia, as 
is well known, is one of the final products of proteid destruction. 
The only known agency that commonly produces the complete 
destruction of proteids is bacterial, and, while the matter has never 
been put to any satisfactory test, the most probable explanation 
seems to be that these cheese flavors are the result of bacterial 
decomposition. 
Against this view, however, has been urged the fact that in the 
well ripened cheeses hardly any bacteria, except lactic acid organisms, 
are present, and that this class of bacteria does not, so far as is 
known, have any power of producing cheese flavors. Some 
bacteria, if they grow in proper abundance in milk, will in time 
develop well-known cheese flavors; but these organisms have not 
been found in old, strongly flavored cheeses. Whether they have 
anything to do with the production of cheese flavors is, therefore, 
uncertain. It has been suggested that the flavor of cheeses may be 
due to the bacteria which grow in them during the first few days. 
Liquefying bacteria are found during this early period, and before 
the miscellaneous bacteria disappear, as they do later, some of these 
liquefiers may secrete from their bodies substances, possibly enzymes, 
that continue their action in the cheese, slowly, but for a long time. 
Although the bacteria that produce them soon die, the chemical 
