
46 STORRS AGRICULTURAL EXPERIMENT STATION. 
Whether or not the straining does have any such influ- 
ence upon the relative proportion of the acid and non-acid 
bacteria, it was evident from further study that this had 
nothing to do with the rapidity of curdling, for the following 
reasons. In most cases, at least, the acid producing species 
which were found in the fresh milk did not continue to grow 
in the milk fora very long time, but after a few hours they 
had entirely, or almost entirely, disappeared. By the time the 
milk was 50 hours old the acid bacteria which were present in 
the original milk had in most cases almost disappeared, and 
another type of lactic bacterium had become very abundant and 
undoubtedly produced the souring and curdling. This species 
is the common acid organism, Bac. lactis acidi. It was present 
in the fresh milk in small numbers only and frequently could 
not be found at all; but in the milk that was 50 hours old and 
milk that was ready to curdle it was present in far the greatest 
numbers. Beyond question the curdling was due to the de- 
velopment of Lac. lactis acidi. Since, therefore, the acid spe- 
cies which were found in the fresh milk did not develop to 
any great extent during the souring, it was clear that the 
relative proportion of acid and non-acid bacteria in fresh milk 
had little or nothing to do with the rapidity of curdling. In 
other words, the presence of a considerable number of acid bac- 
teria in fresh milk is no indication of the keeping quality of 
the milk, nor isit an indication as to the kind of lactic bacteria 
which will be found in the milk at a later period. 
MILK KEPT FOR 50 HOURS AT 70°. 
1. Lotal number.—The study of the bacteria found in the 
milk at the end of 50 hours, in Tables 3 and 4, shows that in 
a majority of cases the strained samples contained at the end 
of 50 hours a somewhat larger number of organisms than did 
the corresponding unstrained samples. ‘The difference, how- 
ever, was not sufficient to have any meaning (503,000,000 
against 454,000,000). 

