102 



BACTERIA IN MILK 



Table XLI 

 BACTERIA IN COW F^CES (Savage) 



in the interval that elapses between sampling and the labora- 

 tory examination. 



Park ^^ took two samples of milk, one containing 3000 organ- 

 isms per c.cm. (agar forty-eight hours at 37° C.) and the other 

 30,000 per c.cm. and stored portions at various temperatures. 

 After various intervals of time the bacterial counts were again 

 taken with the results shown in Table XLII. 



The author has made similar tests but, in addition to the 

 total bacterial count, an estimation was made of the B. coli 

 group by plating on rebipelagar (neutral red bile salt agar) and 

 incubating at 37° C. for twenty-four hours. The total bacteria 

 were counted on 4-1.0 per cent nutrient agar after forty-eight 

 hours incubation at 37° C. 



It will be noticed in both these series of experiments, and 

 especially in Park's, that at the lower temperature there is at 

 first an apparent diminution in the total bacterial count and 

 that this phenomenon is more definite and more prolonged at 

 the lowest temperature used. These observations have been 

 confirmed by many experimenters and led to the hypothesis 

 that milk possessed a weak, though definite bactericidal action : 

 this is usually referred to as the germicidal action of milk. 

 M. J. Rosenau ^^ thoroughly investigated this phenomenon and 

 concluded that no true germicidal action took place, but that 



