1346 Wisconsin Academy of Sciences, Arts, and Letters. 
tube, determining the amount and the formula of the gas pro¬ 
duced, by the action on milk and gelatin, and the production of 
indol. This work was not carried far, however, because of the 
time required and the fact that, to a considerable extent, it 
seemed unnecessary and of less value than other phases of the 
work. This supposition is based on the assumption that bacteria 
producing gas in lactose media are foreign to the best milk, 
and especially unnecessary in pasteurized milk. 
In the poorer grades, belonging to the class “Raw milks,” A lt 
B x and C x (referring to Table VII.) , gas was produced in 
91% of the samples in 0.01 of a c. c. In the remaining cases the 
bacterial count was very low and such did not properly belong 
to this class. In 75% of the samples gas was produced in 0.001 
of a c. c. Two of the non-fermenting samples, in this case also, 
were very low in bacteria. Hence it would seem fair to con¬ 
clude that milks of the grade examined above; i. e., milks which 
are delivered to large pasteurizing plants, are likely to contain 
these lactose fermenters in 0.01 of a c. c., and in the majority 
of instances contain such organisms in 0.001 of a c.c. or, in other 
words, such milks may contain hundreds o*r even thousands of 
such organisms per c. c. 
Milk belonging to this class, but of a better grade, as repre¬ 
sented by E, F 0 2 , and 8 , contain a fewer number of these bac¬ 
teria. K and L are more like the first firoup, namely, A x , B t 
and C 1? but are sold raw. Judged from the standpoint of the 
number of gas bacteria, however, they are better milks. 
If we turn now to the better grades of raw milks we see that 
the gas-producing bacteria, in inspected milks, are less numerous, 
occurring in 1 c. c. portions in 100% of the samples in A 5 , A 6 , 
and B 4 , and in 27% of the cases in 0.01 of a c. c. portion. 
In the remaining groups of Table VII. the total bacterial con¬ 
tent indicates them to be of better quality. B», C 3 , D, G, and M x 
have a much lower percentage of gas-producing bacteria. 
Turning again to the certified milks we see that colon-like 
bacilli are rarely present in 1 c. c. lots, and are never present in 
a fraction of a c. c. 
It appears, then, that the raw milk of Boston contains large 
numbers of bacteria capable of producing gas in lactose media, 
i. e., bacteria belonging to the colon group, in considerable num¬ 
bers in ordinary raw milk (Grade D), fewer numbers in the in- 
