METHODS OF EXAMINING MILK 271 
experienced man is apt to overlook some of them, giving 
an undercount. These difficulties are overcome, how- 
ever, by training and experience. 
COMPARISON OF RESULTS OBTAINED BY THE TWO METHODS 
“ It must be recognized that the results obtained from 
the microscopic record give a closer approximation to 
the actual number of bacteria present in the milk than 
those obtained by the plate method, since the plate 
method will count as one either a single bacterium or a 
group which may sometimes contain a hundred or even 
more individuals. Inasmuch, however, as the plate count 
has become a method of analysis that is well known and 
commonly applied, it becomes desirable to know as closely 
as possible what relations there may be between the plate 
count and the microscopic count. Experience has shown 
that the count of individual bacteria is ordinarily 1.5 to 8 
times as great as the plate count, the ratio between the 
two being largely dependent upon the size of the clumps 
of bacteria present. Where the bacteria are mostly iso- 
lated, the ratio of the two counts would be much closer 
than where there are present long chains of streptococci 
or masses of cocci. After one has had a little experience 
in counting clumps it is found that the number of groups 
shown by the microscope agrees fairly well with the num- 
ber of colonies shown by the plate count, though even here 
there are occasionally discrepancies, due among other 
things to the appearance in the microscope of kinds of 
bacteria which fail to grow in the culture media used in 
making plates. In all cases, however, the direct count of 
raw milk will give a much closer approximation to the 
actual numbers of bacteria than the plate count. In view 
of these facts it is difficult to interpret one count in terms 
