Frost—Bacteriological Control of Public Milk Supplies. 1349 
spec ted grade (B). and that the certified milks are practically 
free from such organisms in 1 e. c. lots. 
The pasteurized milks, A 2 , B 2 and C 2 (Table VII.), produced 
gas, when 1 c. c. of the milk was added to the lactose medium, in 
83% of the cases, and in 25% of the cases in 0.01 c. c. portions 
In certain supplies, as C 2 , it is unfortunate that greater dilutions 
were not planted, since it is quite likely that there might have 
been quite as many lactose fermenters in the pasteurized as in 
the raw milk. (C-l). 
In milks pasteurized in the bottle, A 3 , A 4 , M 2 , these bacteria 
are practically absent in 1 c. c. portions. 
3. The Value of Endows Medium in Milk Work. Endo 
plates were made in a majority of the analyses considered in this 
investigation. The methods employed have already been dis¬ 
cussed and it is necessary here to consider the findings only. 
It was difficult at times to correlate these findings with the data 
obtained from the fermentation tubes. The greatest difficulty 
and indefiniteness come in the better grades of milk, where it 
was necessary to introduce 1 c. c. of the milk into a Petri dish 
In these cases the opacity produced by the milk made the result¬ 
ing growth less characteristic. In recording results no attempt 
was made to give actual counts, because of the frequent appear¬ 
ance of red colonies (not B. coli) in certain of the samples. The 
terms “few” “several,” and “numerous,” have been used 
instead. (See Tables I.-IV. and VII.) It will be noticed that 
in the raw milk (Table VII.), where there are many gas pro¬ 
ducers, there are always several or numerous coli-like colonies 
on the Endo plates, as for example, in A 1? B :l , andCV In those 
samples where fermentation occurs in large quantities of the 
milk (1 c. c.) only, as F 4 , 2 , and 3 , there are also few coli-like 
colonies on the Endo plates. In the inspected milks (Table 
VII.) there is a rather close correspondence between the abund¬ 
ance of gas -producers in lactose peptone bile, and the red colon¬ 
ies on the Endo medium. 
In the certified milks the tests were the same as those obtained 
by the use of lactose peptone bile or in the fermentation-tube 
method. Table VI. of pasteurized milks also shows that similar 
results were obtained by both methods 1 . In milks pasteurized 
in bulk, A.,, B 2 , and 0 2 , coli-like organisms appear in each 
