VARIATIONS IN BACTERIA COUNTS FROM MILK AS AFFEC- 
TED BY MEDIA AND INCUBATION TEMPERATURE 
G. C. Supeitee!, W. A. WaiItinGc, anp P. A. Downs 
The increasing importance of the liquid-milk supply for large centers 
of population and the greater demand for a better quality of raw mater- 
jal for manufacturing purposes have necessitated ‘further knowledge of 
the methods used in determining the quality of milk, and particularly 
have emphasized the significance of bacteriological analyses. 
Examination of milk for the purpose of determining numbers or types 
of bacteria seems to constitute the highest ideal in milk grading. This 
aspect is doubtless important and the respect for this method of procedure 
in judging milk quality should not be endangered. Obviously, the sani- 
tary aspects of the milk problem must involve determinations of this kind. 
The significance of bacteria in the economic phases of the milk supply 
also becomes quite clear when it is remembered that the entire business of 
supplying milk to the urban population is founded on modern dairy 
- science, of which the aims are maximum wholesomeness and maximum 
_ keeping quality. These two considerations have been responsible for 
the stress laid on the importance of bacteria counts in the milk industry 
at the present time. 
That the methods of enumerating bacteria in milk have many short- 
comings is well recognized by dairy bacteriologists. Bacteria counts, 
as now obtained, can be interpreted only on a comparative basis, and in no 
sense do they indicate the mathematical accuracy which their expression 
in numbers implies. Such comparative interpretations can be used only 
as indications of degrees of success in handling and of the variations of 
keeping quality. Undeniably this information is valuable in safeguarding 
the interests of consumers of milk in large cities, and its importance is 
shown by the report of the Committee on Statistics of Milk and Cream 
Regulations of the Official Dairy Instructors’ Association (1917). This 
committee obtained the complete milk regulations from 409 cities and 
1At present Director of Research Department of the Dry MilkjCompany, New York. 
*Dates in parentheses refer to Literature Cited, page 247. 
221 
