22 THE BOOK OF CHEESE 



34. Germicidal effect of milk. Authorities agree 

 that when a bacterial examination of the milk is made, 

 hour by hour, beginning as soon as it is drawn from the 

 cow, there is no increase in the number of organisms for 

 a period of several hours at first, but an actual reduction 

 not infrequently takes place. This is called the " germi- 

 cidal " 1 property of milk. The lower the temperature 

 of the milk, the longer and less pronounced is the germi- 

 cidal action; the higher the temperature, the shorter 

 and more pronounced is this action. 



This is explained as either: (1) a period of selection 

 within which types of bacteria entering by accident and 

 unadapted for growth die off ; or (2) an actual weak anti- 

 septic power in the milk-serum itself ; or (3) the forming 

 of clusters by the bacteria and so reducing the count. 



In working on a small scale or on an experimental 

 basis, this property at times introduces a factor of 

 difficulty or error which is not to be lost sight of in the 

 selection of the milk for such purposes. 



35. Sources and control of bacteria in milk. Most 

 of the bacterial infection of milk is due to lack of care 

 in handling. Some of the common sources 2 of con- 

 tamination are : the air in the stable ; the cow's body ; 

 the milker; the utensils; the method of handling the 

 milk after it is drawn from the cow; unclean cheese 

 factory conditions. 



1 Hunziker, O. F., Germicidal action of milk, N. Y. (Cornell) 

 Exp. Sta. Bui. 197. 



Stocking, W. A., Germicidal action of milk, Conn. (Storrs) 

 Exp. Sta. Bui. 37, 1905. 



U. S. Treasury Dept., Hygienic Laboratory, Bui. 41, Milk 

 and its relation to the public health, 1908, also revised as Bui. 

 56, 1909. 



2 U. S. Dept. Agr., Farmers' Bui. 602, Dairy Division, Pro- 

 duction of clean milk, 1914. 



Lauder, A., and A. Cunningham, Some factors affecting the 



