

APPLICATIONS OF BACTERIOLOGY IN EUROPE. 95 
“fermentation test” designed for the purpose of enabling 
the cheese-maker to exclude from his cheeses any milk which 
is likely to produce trouble. Its application is extremely 
simple, and there have already been devised and put upon the 
market forms of apparatus which make it convenient to use 
in ordinary cheese factories. It consists simply in testing 
separately samples of milk from each patron. The essence of 
the process is merely this: A small sample of the ordinary 
milk is put in a special vessel by itself, and is then subjected 
to a moderately warm temperature and carefully watched. If 
the milk is found to curdle in a proper time in a normal fash- 
ion it is regarded as perfectly safe to use; but if the milk be- 
comes full of gas bubbles in the curdling, if the nose or the 
tongue detects any specially unpleasant or unusual qualities, it 
is inferred that the milk is filled with bacteria that will be de- 
leterious to the process of cheese-making. When this occurs 
the milk from the sources from which the sample is taken is not 
allowed to be mixed with the ordinary milk for the purpose of 
making the cheese. This fermentation test is not used very 
widely. As a rule cheese is made to-day practically as it was 
fifteen years ago, before any knowledge of bacteriology was 
obtained. But cheese-makers have learned that this fermen- 
tation test may be used at time of trouble and may be used 
as a means of discriminating milk that can be safely put into 
cheeses from that which it is not safe to use in this way. The 
practical difficulty in the way of the test is, of course, that the 
cheese-maker may not discover until weeks after the cheeses 
are made that they are likely to develop certain undesirable 
faults, and by this time the fermentation test is of comparatively 
little use. The original source of error has very likely disap- 
peared, and the application of the fermentation test after the 
discovery that the cheeses are liable to “faults ” is too late 
to be of much use. Nevertheless the fermentation test has 
been in some cases found to be of practical value. 
The success of the use of pure cultures in improving. the 
quality of butter, and the manifestly close relation between the 
form of fermentation in ripening cheese, and the character of 
the cheese, suggests, of course, a very great possibility of the 
application of pure cultures to the process of cheese-making. 
If it is true that the, flavors of different kinds of cheeses are due 
to different species of bacteria or moulds, it ought to be possible 
to use pure cultures of the proper species in such a way as to 
give rise to perfect uniformity in the results, and to make it 
