18 STORRS AGRICULTURAL EXPERIMENT STATION. 
of the characteristic species are isolated with great difficulty 
from cream by the use of ordinary gelatin, but are found with 
the greatest of readiness by the use of sugar gelatin. Practi- 
cally also it has been found extremely useful to employ for this 
purpose only gelatin which has been rendered blue with litmus 
solution, as this makes it possible readily to distinguish the 
acid organisms from those that do not produce acids. It has 
been found that one species of bacterium which. is par excel- 
lence a dairy species, namely &. aczdz lactictz, No. 206, produces 
in such gelatin a colony which is most readily distinguished 
from any other species of bacteria, and this of course makes it 
extremely convenient for use. 
After isolation of the bacteria they have been purified by 
replating in the customary manner, and then inoculated into 
the ordinary media for the purpose of determining their char- 
acteristics, which have been obtained as usual. Special atten- 
tion, however, has always been given to the effect of the 
organisms upon milk at ordinary room temperature and at 
higher temperatures. In many cases also the action of the 
organisms upon sterilized cream has been determined, and in 
a considerable number of the cases the influence of the organ- 
isms upon the character of the butter obtained from cream 
ripened by means of them has been made out. 
Unfortunately, the use of the fermentation tube has not been 
adopted so widely as would be desired. In the study of some 
species the fermentation tube has been used, but in the majority 
of cases it has not. In the work that is done now it is used 
in all cases, but in many of the descriptions which have been 
given in past years this important test was omitted. For this 
reason the production of gas in glucose bouillon has not been 
determined in many cases. In determining the characteristics 
of these bacteria no attempt has been made to determine their 
action upon nitrites or the production of indol, nor has any 
attempt to determine pathogenic characteristics been made. 
These features have not yet been regarded as of significance 
enough in the study of dairy bacteria for dairy purposes to 
warrant the time which would be taken in determining them. 
GROUPING THE BACTERIA. 
In dividing the dairy bacteria into groups I have tried so far 
as possible to follow the methods already adopted, and have 

