538 WILLIAM H. CHAMBERS 



much weaker agglutination than Culture R and a strong germi- 

 cidal reaction. If the decrease was only apparent, owing to 

 agglutination, one would expect to find by microscopic count in 

 the comparable raw and heated milk approximately equal num- 

 bers of individual bacteria clumped in the raw milk and evenly 

 distributed in the heated milk preparation. Such is- not the case. 

 The shaking of the samples and dilutions was uniform and vigor- 

 ous (thirty times) and a comparison of the plate count and the 

 ratio of clumps in the raw milk to individuals in the heated milk 

 would indicate that the clumps were broken up. For example, 

 a typical case with Culture R showed a plate count ratio of 46 to 

 100 (raw to heated), and the corresponding stained preparation 

 showed a ratio of 1 to 100 (clumps to individuals). With Bad. 

 coli (table 2, column 2) the microscopic count and plate count 

 check very closely The microscopic examination at 120 min- 

 utes showed three small clumps in the raw milk in the entire 

 preparation of 0.01 cc, or approximately 7500 bacteria per cubic 

 centimeter, and in the heated milk preparation an average of 1.5 

 bacteria per microscopic field, or approximately 1,500,000 bac- 

 teria per cubic centimeter. This compares very favorably with 

 the plate count of 10,400 per cubic centimeter in the raw milk 

 and 1,035,000 per cubic centimeter in the heated milk (table 2, 

 column 2, 120 minutes). Evidently there is an actual decrease 

 of bacteria with Bad. coli as shown by the plate count and the 

 microscope. It is of interest to note the similarity in germicidal 

 action in the growth curves of Bad. coli in raw milk (chart 1) and 

 Bad. coli in normal rabbit-serum (Chick). 



In the freshly drawn mixed milk from a herd of cows the ac- 

 tion of bacterial inhibition is variable because of its specificity. 

 The numbers of species of organisms increase as contaminations 

 from the cows, barn, utensils, etc., are added to the original udder 

 flora. Where only the total number of bacteria in the milk is 

 considered, a decrease in numbers may be evident, or one unaf- 

 fected strain by its rapid increase may completely hide the germi- 

 cidal action on another less numerous strain, particularly if the 

 action is caused by only a few cows. The predominance of the 

 lactic acid organisms with the increasing age of the milk might be 



