"Petruschky and Kriebel 11 and Hoi ling 1 see in the streptococci 

 found in milk a cause of summer diarrhea in children." 1 



It is not surprising that streptococci from an active disease 1 

 process in the glands of the cow are able to exert a pathogenic 

 influence when introduced into man and the lower animals. The 

 significance of streptococci from such a source is not necessarily 

 the significance of streptococci isolated from milk of normal. 

 healthy udders. In the latter case Ave have a nonpathogenic 

 germ, the exact relation of which to the pathogenic streptococci 

 is not known. If these organisms are attenuated forms of the 

 pathogenic streptococci, it is possible that under favorable con- 

 ditions their pathogenicity may be restored and we may then 

 attach to them considerable importance. The significance then 

 of the common milk streptococci, so far as the health of the 

 consumer is concerned, depends upon their relation to the strep- 

 tococcus pyogenes. 



PURPOSE OP THE INVESTIGATION. 



This investigation was undertaken to determine the frequency 

 of the occurrence of these streptococci iji milk and their relation 

 to streptococcus pyogenes. 



METHOD OF INVESTIGATION. 



The ordinary method of isolation by means of plate culture 

 was employed in obtaining strains of the milk streptococci. 

 They were then grown on gelatin, agar, potato, milk, and 

 Lofflers blood-serum and comparison made with similar cultures 

 of a strain of streptococcus pyogenes which was originally ob- 

 tained front, the Marine Hospital Service. Those showing cul- 

 tural similarity to the latter organisms were retained for fur- 

 ther study. 



THE MILK STREPTOCOCCI. 



The common lactic bacteria were formerly classified in three 

 groups : 



1. Bacterium Aerogenes. 



2. Bacterium Acidi Lactici. 



3. Streptococcus Lacticus. 



