62 Kansas Academy of Science. 



count, concluded that the number of bacteria in separated 

 cream decreases proportionally as the fat content increases 

 and the number of bacteria in separated milk decreases pro- 

 portionally with the increase of fat in the cream. 



The importance of this subject from the commercial, sani- 

 tary and scientific standpoints led to this investigation. 

 Briefly stated, the object of the study was to determine : 



1. The distribution of the bacteria in the cream, skim milk 

 and bowl sediment. 



2. The effect of separation upon the number of bacteria in 

 the mixed milk. 



3. The effect of different separators upon the distribution 

 of bacteria. 



4. The influence of mechanical conditions, such as the per- 

 cent of butter fat in the cream, upon the distribution of 

 bacteria. 



5. The distribution of various types of bacteria by the 

 separator. 



6. The effect of distribution upon the keeping quality of the 

 milk. 



EXPERIMENTAL DATA. 



The samples of unseparated milk were taken just before 

 separating, and the samples of cream, skim milk and mixed 

 milk just after. The time which elapsed between collecting 

 and plating was not more than ten or fifteen minutes. 



Standard plain meat-juice agar was used, and all plates in- 

 cubated at room temperature for four days and counted. An 

 average of all countable plates was taken, and the results are 

 comparable. 



In all cases the tests were run at the best conditions (speed 

 of separator and temperature) for skimming. Care was taken 

 to sterilize all the utensils, including all containers, separators 

 and other utensils in streaming steam before using. This was 

 done in order to avoid any errors which m.ight arise from con- 

 tamination and the resulting irregularity from such data. 



Table I indicates what effect contamination might have upon 

 the results. Several liters of sterile water were poured through 

 the separator and samples of the water taken after passing 

 from the cream spout and from the skim-milk spout of the ma- 

 chine. 



