68 STORRS AGRICULTURAL EXPERIMENT STATION. 
It is evident then that both for the industry of furnishing 
sweet milk to cities and for the butter-making industry, an 
accurate knowledge of the source of the lactic bacteria is desir- 
able. ‘Io determine if possible the actual source of these 
organisms was the object of the experiments here reported. 
EXPERIMENTS ON THE SOURCE OF THE LACTIC ORGANISMS. 
In the investigations reported in the following pages the 
effort was made to discover particularly the source of B. aczdz 
lactici, inasmuch as this has proved to be the most widely 
distributed of the lactic bacteria and the one which forms 
ordinarily over 90 per cent. of the bacteria in ripened cream. 
Secondarily, attention was also turned to the source of the 
two other lactic organisms. Previous to the work of Esten no 
definite suggestions were made as to the source of these organ- 
isms. Esten made a few experiments to determine whether 
the organism which he isolated came from hay or dust or from 
the teats of the cow. In his experiments neither hay nor the 
dust of the cow stall gave him any evidence of the presence 
of the B. acidi lactici. "This fact, together with some other 
experiments, suggested to him the possibility that the natural 
home of the organism in question was the milk duct; but these 
organisms have not been found hitherto in the udders of cows 
when these have been examined bacteriologically. It is pos- 
sible, however, that they have escaped the attention of those 
who have examined the udders, because of difficulty of detect- 
ing them with ordinary culture media. Moreover, as indicated 
above, B. acidi lactict has not been found very abundant in 
fresh milk or cream, although apparently universally present 
in large numbers in ripened cream. It may be, however, that 
the bacterium was present in small numbers even in freshly 
drawn milk, but escaped observation on account of difficulty of 
investigation. ‘To determine whether or not this organism is. 
actually present was one particular purpose of the following 
experiments. , 
GENERAL DESCRIPTION OF EXPERIMENTS. 
Three different series of experiments have been made, the 
first two consisting of the studies of milk as drawn directly 
from the cow, and the third consisting of a bacteriological. 
