2 BULLETIX 303, U. S. DEPARTMENT OF AGEICULTUEE. 
Bacterial counts, while of value, only tell us the numbers, and this 
is not sufficient information. It is necessary for a thorough knowl- 
edge of the subject to know the kinds of bacteria which are generally 
present in ice cream as well as the number. 
There is relatively little exact information regarding the bacte- 
riology of ice cream, and in consequence probably many applications 
of the subject to the industry are neglected. Extensive research 
work on bacteriological problems connected with the manufacture of 
ice cream is needed, and it is probable that many investigators will 
devote themselves to this subject when the value of such work is 
realized. 
Our investigations on the general subject of the bacteria of ice 
cream will be divided into three main parts. 
1. A study of the number and kinds of bacteria in commercial retail 
ice cream as the consumer receives it. 
2. A study of the bacteriology of ice cream during manufacture. 
3. A study of the development of bacteria in ice cream during 
storage. 
These studies have been undertaken solely with the idea of securing 
information of fundamental importance relative to the bacteriology 
of ice cream. We hope by these investigations to be able to give the 
manufacturer information which will enable him to produce a product 
of the highest quality. 
We believe that bacteriology will be of great value to the manufac- 
turer in controlling the quality of his raw material and the quality of 
his final product, and -in checking the efficiency of the various opera- 
tions in the production of ice cream. 
OBJECTS OF THIS INVESTIGATION. 
The first part of our investigations is presented in this paper, the 
objects of the work being as follows: 
1. To determine the number of bacteria in commercial ice cream 
during the summer and winter seasons. 
2. To determine what groups of bacteria are found in commercial 
ice cream. 
3. To determine the relative value of different methods for the de- 
termination of Bacillus coli in ice cream. 
METHODS OF EXAMINATION. 
The ice cream was purchased in one-half -pint paper boxes from 
various stores throughout the city of Washington, D. C. Throughout 
this paper reference is made to summer and winter samples. The 
samples of the former were collected from June 20, 1912, to Novem- 
ber 11, 1912. Winter samples were obtained during February and 
March, 1913, the coldest months of the year in Washington. The 
