94 STORRS AGRICULTURAL EXPERIMENT STATION. 
had developed for six or seven days. Occasionally the pres- 
ence of rapid liquefiers made it necessary to study the plates 
somewhat earlier. Experience has shown that the various 
species can be differentiated much more accurately when the 
colonies have developed for about a week, and it was for this 
reason that the plates were studied at this time, though the 
total numbers might have been obtained somewhat sooner.« 
When the plates were properly developed, they were carefully 
studied and the following determinations made: 
1. The total number of bacteria. 
The total number of acid producing bacteria. 
The total number of non-acid bacteria. 
The total number of liquefying bacteria. 
nf ® N 
The predominating species. 
In each experiment the predominating species in the acid 
producing group, and also in the non-acid group, were isolated, | 
and later were carried through the various cultures in order to 
identify the species. This was necessary in order to determine 
definitely whether or not certain species disappear, while others 
increase, during the period covered by the so-called ‘‘germicidal 
action;’’ and special care was taken to determine the acid species 
present. 
It will be seen by a study of the results obtained that this 
work of differentiating types of organisms, especially of the 
lactic acid producing ones, was especially important, since it 
reveals the fact that certain species are not affected by the 
germicidal theory, while others are decidedly so affected. 
About twenty experiments have been conducted, and the 
results are quite uniform. In almost every case there is a fall- 
ing off in the total number of the organisms present, during 
the first few hours. This will be seen by a study of Tables 28, 
2omand 20: 
NUMBERS OF BACTERIA DECREASE. 
It may be seen by a study of these tables that in nearly all 
cases there appears to be a reduction in the number of bacteria 
during the first few hours after the milk was obtained, or, in 
other words, nearly all of the milk tested showed the presence 
