THE BACTERIA FOUND IN MILK 33 



This table shows that the results obtained with milk 

 samples from individual cows approximate more closely to 

 those obtained with mixed milk samples than to the cow- 

 dung or human faeces results. The chief differences are in 

 regard to the fermentation with salicin and rafh'nose. 



The pathogenicity test for streptococci isolated from milk 

 is probably a test of considerable value if carried out immedi- 

 ately after isolation. The writer tested the pathogenicity of 

 25 streptococci isolated from the milk cistern and teats of 

 healthy cows. In every case the results were negative. 

 Streptococci isolated from mixed milk also proved negative. 

 On the other hand, streptococci isolated from milk supposed 

 to be causing sore -throat or other human disease have on 

 several occasions been found to be pathogenic to mice. 



Heinemann l investigated the virulence upon rabbits of 

 a number of streptococci obtained from milk. The initial 

 results were usually only slight local reaction at the seat of 

 inoculation, but by passing the streptococci through a series 

 of rabbits a high degree of virulence was acquired. After five 

 or more passages, subcutaneous injections became fatal in doses 

 of 2 c.c. of 24-hour-old broth cultures. The virulence approxi- 

 mates to, if not equals for this animal, that of typical Strepto- 

 coccus pyogenes from human affections. Heinemann remarks : 

 " The lesions produced by Streptococcus lacticus in rabbits are 

 of the same kind and extent as those produced by Streptococcus, 

 pyogenes from pathological conditions in human beings." 



Staphylococci. This group of organisms is abundantly re- 

 presented in milk. They are particularly abundant, indeed, 

 in the writer's experience, nearly universally present, in milk 

 samples drawn direct from individual cows and without chance 

 of outside contamination. A number of different varieties 

 may be recognised by appropriate tests. Our present knowledge 

 is sufficient to enable us to say that, in general, their presence 

 is without pathological significance. 



GROUP 2. BACILLUS COLI AND ALLIED ORGANISMS 



In this group are included a number of lactose fermenting 

 organisms of which Bacillus coli communis is the type, but which 



1 Journ. of Infect. Diseases, iv. p. 87, 1907. 



