CLASSIFICATION OF DAIRY BACTERIA, 17 
bacteria should be comparable with each other. It is, how- 
ever, at present unavoidable, because most of these species 
have not been preserved in culture in the laboratory, and it is 
now impossible to determine the characteristics which have not 
hitherto been made out. For these reasons the tables which I 
have been obliged to make out and to use differ in some details 
from those of Fuller and Johnson. I have, however, followed 
them as closely as possible. 
SOURCHS OF “DHE SPECIES. 
A word as to the sources of the different species of bacteria 
which are here described. All have been obtained from dairy 
products. A majority of them have come from cream either 
from neighboring creameries or from private dairies, some | 
being obtained from ripened cream, others from unripened 
cream. Some of them have been obtained from milk as deliv- 
ered in Middletown by milkmen. Some have been obtained 
from the milk after it has stood in the pantries of private 
houses. Some of the species have been obtained directly from 
milk as drawn from the teats of the cow into sterilized vessels, 
others again from the dust which falls into the milk pails 
during the milking. ‘Two of these species have been obtained 
from some samples of special milk which had been sent in cans 
from Uruguay; and some of the species have been obtained from 
samples of milk that were sent to Middletown from a large num- 
ber of States in the Union, ranging from Maine to California. 
All, however, are strictly dairy organisms, being found in milk 
or its products. 
METHOD OF ISOLATION AND STUDY. 
The method of isolation and study requires little description, 
inasmuch as it has been, in general, that commonly used in 
bacteriological study. For the isolation of the bacteria from 
the milk ordinary gelatin has been used. In most of the early 
years the gelatin was made in the ordinary way, but in recent 
years it has been found that a much more satisfactory result is 
obtained if there is added to the gelatin three per cent. of milk 
sugar. The reason for this is manifest. Milk always contains 
a considerable portion of milk sugar. Naturally, therefore, it 
is to be expected that the typical dairy bacteria will grow much 
more rapidly in gelatin provided with milk sugar. Indeed, some 
