New York Agricultural Experiment Station. 107 



accuracy of all of the data presented in this portion of the publica- 

 tion. 



Method of classification. — The attempt at separating and de- 

 scribing the forms of bacteria which occur in cows' udders meets 

 the difficulty common to an attempt at such a classification in any 

 division of the bacterial flora, the lack of a satisfactory system of 

 classification. 



The older system of classification, which was widely applied 

 to this class of bacteria by Conn, Esten and Stocking, 14 proceeded 

 on the assumption that bacteria were especially prone to vary in 

 their physiological activities and accordingly the groups into which 

 they might be arranged must have shadowy and uncertain limits. 



The newer system of the Society of American Bacteriologists 

 accepts the division into genera according to the classification of 

 Migula. It proceeds on the assumption that the members of each 

 genus can be reduced to groups, the members of each group 

 agreeing exactly in the possession of or the lack of certain 

 physiological functions. A novel feature in this system is the 

 provision for expressing these functions numerically. By writ- 

 ing these numbers in a definite order the most important phy- 

 siological activities of the organism in question are expressed 

 tersely and in a form which is most favorable for direct com- 

 parison. By arranging many such numerical expressions in order, 

 those with identical physiological functions are grouped together 

 and the numerical expression which characterizes the group be- 

 comes their " group number." 



While this newer system substitutes scientific accuracy for the 

 hazy generalizations which characterized the older, in its present 

 form it can hardly be considered as fully perfect. Its manifest 

 advantage as a means of tersely recording the observed facts re- 

 garding the isolated cultures led to its use in these studies. 



The numbers used in recording various important physiological 

 reactions were as follows : 



14 Conn, H. W., Esten, W. M., and Stocking, W. A. A classification of 

 dairy bacteria. Conn. (Storrs) Agr. Exp. Sta. Ann. Rpt. 18 ( 1906) : 91-203. 

 1907*. 



