294 REPOKT UF OFFICE OF EXPERIMENT STATIONS. 



BACTERIA IN MILK. 



Jiactoiiu iiiv so intimately associated with every phase of dairying 

 that this subject has naturally received niuch attention in station 

 ^vork. 'J1ie sources of bacteria in milk have been studied and the 

 fermentations produced by various species have been investigated. 

 Particular attention has been paid to the prevention of bacterial con- 

 tamination, and methods of destroying or delaying the development 

 of the organisms that do gain access to milk have been repeatedly 

 testetl. This subject has been treated frequently in bulletins of a 

 more or less popular nature, among which are the following: Milk: 

 Its Decomposition and Preservation, by R. R. Diinviddie; " The Re- 

 lation of Temperature to the Keeping Property of Milk, by H. W. 

 Conn; ^ Bacteria and the Dairy, by C. E. Marshall; " Cleanliness in 

 Handling Milk: Bacteriological Considerations, by H. L. Bolley;'* 

 Bacteriology of Milk, by L. L. Lewis.^' • 



The investigations of Ward f showed that bacteria are regularly 

 present in the interior of the udder, and that milk, although sterile 

 when secreted by healthy glandular tissue, may become contaminated 

 immediately by the bacteria normally present in the smaller milk 

 ducts. This work furnished an acceptable explanation for the fail- 

 ures invariably met with in attempts at securing iiny considerable 

 quantity of milk uncontaminated by bacteria. AVliile the bacteria 

 found by "Ward in the interior of the udder did not seem to affect 

 milk seriously and was therefore unimportant as regards the keeping 

 qualit}^ of the milk, the results of the investigations did not, ag 

 remarked by the author, preclude the probability that forms more 

 injurious to milk may invade the ndder. 



Pernot^ endeavored to ascertain if the bacteria commonly found 

 in stagnant water can gain access to the milk supply through the 

 cow. Pure cultures of several of such organisms Avere added to the 

 drinking water and given daily for ten-day periods. In no instance 

 were the organisms recovered from the milk produced. Continuing 

 these experiments with drinking water, 10 cubic centimeters of a 

 bouillon culture of the typhoid bacillus w^as given to a cow daily for 

 ten days, and 20 cubic centimeters daily for the five days following. 

 The results failed to show that typhoid bacilli can gain access to milk 

 in this way. It was also desired to determine if typhoid bacilli are 

 able to enter the udder through the teat when cows wade in water 

 containing this organism. The teats were therefore immersed in a 

 pure culture immediately after milking and allow^ed to dry spontane- 



o Arkansas Sta. Bui. 45. «-' Oklahoma Sta. Bui. 40. 



6 Connecticut Storrs Sta. Bui. 26. f New York Cornell Sta. Bui. 178. 



c Michigan Sta. Bui. 146. c Oregon Sta. Bui. 71. 



d North Dakota Sta. Bui. 21. 



