Journal of 



Applied Microscopy 



and 



Laboratory Methods 



Volume V. NOVEMBER, 1902. Number 11. 



The Bacterial Flora of Freshly Drawn Milk. 



I. 



The constant presence of bacteria in freslily drawn milk is a matter of con- 

 siderable importance, and this fact goes a long way in explaining the ineffectual 

 attempts to obtain milk in commercial quantities uncontaminated by bacteria. 

 At the same time, it has been but very recently that investigations as to the 

 number and nature of the organisms that gain access to the milk through their 

 localization and multiplication in the milk ducts have been made. The first re- 

 corded experiments are those of Leopold Schultz^ in 1892. He examined milk 

 bacteriologically at the first milking, in the middle of the milking, and at its 

 close. This examination consisted merely in counting the number of bacteria 

 present ; and, as a result, the following figures were determined : The first milk 

 contained from 55,000 to 97,200 germs per c. c, the middle milk from 2000 to 

 9000 germs per c. c, and the last milk was in some cases sterile, and sometimes 

 contained about 500 germs per c. c. The number of germs in the last milk he 

 says depended upon the quickness with which the milking was done. When 

 done quickly, all the germs were washed out, so that " the last milk was often 

 but not always sterile." 



Gernhardt,^ investigating the same subject, found a larger number in samples 

 from the middle of the milking than at the beginning. To explain this result 

 as well as to explain irregularities in the numbers, he suggests that the bacteria 

 made their way up through the milk ducts of the teats, through the cistern and 

 into the smaller ramifications of the ducts which connect the cistern with the 

 ultimate follicles. As many of the colonies so formed are not easily removed, 

 they are not found in the first milk, but appear later when they have become 

 broken up by the movements of milking. 



Von Freudenreich,-^ on the other hand, states that when in the udder, milk is 

 free from bacteria except when the milk glands are in a diseased condition. 



H. L. Bolley and C. M. Hall,^ in their studies of the bacterial flora of the 



(2029) 



