THE GERMICIDAL ACTION OF FRESH COW'S MILK 



In the preceding chapter it has been shown that antibodies of 

 various kinds may be transmitted to the milk from the circula- 

 tion. Therefore it is not surprising that many investigators be- 

 lieve they have demonstrated an actual germicidal property in 

 fresh cow's milk. 



It has been noted that there is no increase of bacteria in the 

 milk while in the udder. On the contrary, when cultures of bac- 

 teria have been injected into the udder, it has been difficult to 

 recover them after the lapse of some time. Furthermore, it is 

 generally assumed that bacteria actually present in the udder 

 have gained access from the outside. If this is true, it is natural 

 to expect to find a variety of species in the milk while in the 

 udder; as a matter of fact, however, micrococci are predominant, 

 while other species are exceedingly scarce, indicating that there 

 is some restraining influence at work in the udder which perhaps 

 persists for some time after the milk has been drawn. This influ- 

 ence may affect different kinds of bacteria to a greater or lesser 

 degree, and this assumption would explain the dying off of most 

 species, while micrococci are but slightly restrained. But even 

 micrococci are present in relatively small numbers, considering 

 the fact that a good food substance and a favorable temperature 

 furnish good conditions for growth in the udder. 



It has been assumed by some that the leukocytes are respon- 

 sible for the disappearance of bacteria in the udder. This view 

 has been advocated chiefly by Rullmann and Trommsdorff, who 

 have stated that there is a definite relation between the germicidal 

 property of fresh milk and its cellular content. Rosenau and Mc- 

 Coy do not agree with this view, but believe they have demon- 

 strated that the germicidal property of milk is independent of the 

 number of cells present. However, Luckhardt and others have 

 shown clearly that phagocytes actually occur in milk not uncom- 

 monly, although it has not been shown whether the number of 

 bacteria disposed of by phagocytosis is sufficiently great to cause 

 a decided decrease. 



Fokker was the first to suggest the presence of bactericidal 

 substances in fresh milk. He drew goat's milk under aseptic 

 precautions and boiled one portion of it. After inoculating both 

 the boiled and raw milk with lactic acid bacteria he found that 

 the boiled milk turned sour before the raw milk did. He con- 



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