1342 Wisconsin Academy of Sciences, Arts, and Letters . 
on the better grades of milk. The milks pasteurized by this 
method all belong, theoretically, to the inspected class, and are 
much better milks than those used for pasteurization in hulk. 
Compare counts of A 5 A e , and M 1? in this connection. 
c) Inspected Milks —Class B. 
Inspected milks should contain less than 100,000 bacteria per 
c. e. according to the Milk Commission. 
Eight different milks of this grade have been examined. A 5 
and A 6 run high; both of these, however, are afterwards pasteur¬ 
ized in the bottle. See A s and A 4 , B 3 , D, G, and M were very 
good milks and were always well under the above limit. B 4 and 
C 3 were not nearly as good, but satisfactory from this standpoint 
in practically one-half of the samples examined. 
d) Certified Milks —Class A. 
The certified milks have a limit of 10,000 fixed by contract, and 
it is quite certain that any excessive count would be only tem¬ 
porary. Table V. gives the results obtained. 
e) General Considerations. 
The technique used for determining the bacterial content was 
the Committee’s, except that the temperature of incubation was 
that of the room (21° C.) instead of 37° C., as recommended 
by them. My object in making this change is a feeling gained 
from a rather long experience that the number of bacteria grow¬ 
ing into colonies at this lower temperature much more nearly 
corresponds to the total number present than when the incuba¬ 
tion is at the body temperature. What I wanted in this particu¬ 
lar study was to get the total number of bacteria present, as 
nearly as possible, since I hoped to detect and estimate quanti¬ 
tatively the fecal forms by other methods. Hence the numbers 
representing the total number of bacteria per c. c. is somewhat 
higher than that likely to be obtained by one who follows exactly 
the standard methods. 
In this connection a phenomenon of much importance was ob¬ 
served which needs consideration here. It relates to the rate of 
growth of colonies of bacteria on plate cultures made from milks 
of varying degrees of purity. This is especially noticeable when 
the rate at which colonies develop from raw milks on agar plates 
is compared with the rate at which colonies develop on agar 
plates when seeded with pasteurized or certified milks. 
