PRELIMINARY NOTE ON THE CLASSIFICATION OF 

 SOME LACTOSE FERMENTING BACTERIA 



MAX LEVINE 

 From the Bacteriological Laboratories of the Iowa State College, Ames, Iowa 



Received for publication, July 22, 1916 



The key given below is the result of a study of 333 lactose 

 fermenting organisms isolated from soil, sewage, and various 

 animal sources, including man, the horse, the sheep, the cow, 

 and the pig. 



The fermentation reactions were determined in peptone water 

 containing the test substance. 



Motility was observed in a soft agar medium (nutrient broth 

 with 0.5 per cent agar) after six, and twenty-four, hours incuba- 

 tion at the body temperature. Six hours seems sufficient for 

 differentiation. 



Gelatin liquefaction was recorded for five weeks. 



The methyl red and Voges-Proskauer reactions were deter- 

 mined in 0.5 per cent glucose-peptone-dipotassium phosphate 

 solution. 



It will be observed that the subdivisions are not based upon 

 single characters, but upon differences in groups of characters. 

 Where inspection is impractical, or insufficient to show which 

 character is best correlated with others, considerable informa- 

 tion may be obtained from a study of the coefficients of corre- 

 lation. That character which gives the highest coefficient of 

 correlation with the greatest number of characters studied is 

 the best for classification, if subdivision is to be made entirely 

 upon correlated characters. 



It should perhaps be noted that the names assigned to the 

 species in the key are tentative, and may be changed, if upon 

 further study of the hterature, they are found to be invaUd. 



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