62 REPORT OF DEPARTMENT OF BACTERIOLOGY OF THE 
CLASSIFICATION. 
A convenient and rapid method of reducing unknown cultures to 
clear-cut and closely related groups is the end toward which bacteri- 
ologists are striving. The more nearly these groups approximate 
our present conception of species the better. 
An attempt at classifying dairy bacteria was made in 1899 by 
Conn.18 He separated them into Io groups, 3 of which were 
characterized by their chromogenesis—red, orange and yellow 
forms. The remaining organisms were divided into 7 groups on the 
basis of their morphology, liquefaction and spore formation. These 
characteristics could be quickly determined (in many cases the 
assignment to groups could be made from the original plates) but 
owing to the small number of groups the final problem of classifying 
the members of a group was not an easy one. 
In 1g06 Conn?® brought out a more detailed classification of dairy 
bacteria which recognized 115 groups and about 160 types. In this 
connection he disavowed any attempt to make use of the term 
syecies. This publication marked a distinct advance in the knowl- 
edge of the subject and it has been of much assistance to us in our 
study of the cheese flora. The described types cover the field so 
completely that among the large number of cultures isolated in con- 
nection with our present study all but one were included in Conn’s 
list. 
The principal criticism of his system as it now stands is that 
many of the types are too inclusive. Our accumulation of cultures 
of a single type in one case amounted to nearly 100 and they 
naturally fell into a number of subtypes. - Even with a much smaller 
number of cultures well marked differences were observable. One 
type, Micrococcus varians, is well named; since the seven cultures 
which were studied are distributed among four different group num- 
bers. Exception might also be taken to some of the characteristics 
used in separating groups. Viscosity, character of colony growths, 
and the character of the curd produced in milk seem to us as most 
open to the objection that discordant results would probably be ob- 
tained by different workers. ) 
Conn’s classification is an adaptation to bacteria of the conven- 
tional botanical description accompanied by a key quite similar to 
that in Gray’s Manual. Simultaneously there has been taking form 
See note 4. 
7 See note 5. 
