52 REPORT OF DEPARIMENT OF BACTERIOLOGY OF THE 
enabled us to extend our studies to the product of their respective 
factories. 
Our colleague, Mr. Geo. A. Smith, has materially aided us both 
by the preparation of experimental cheeses and by the scoring of 
those obtained from the above sources. This parallel study of 
the flora and of the commercial quality has been one of the most 
interesting features of this investigation and it was only made pos- 
sible by the cordial assistance of Mr. Smith. 
We are also deeply indebted to Dr. H. W. Conn, whose recent 
studies of dairy bacteria have especially fitted him to criticise these 
results and who has been so kind as to give us the benefit of his 
point of view. 
HTSTORICAT: 
Studies of the bacteria in cheese have, uniformly, been conducted, 
and in most cases have been described, as incidental to the larger 
question of cheese ripening. At times these two questions have 
been considered as identical. . 
While the work of Duclaux® marks the real beginning of the 
attempt to sort out and arrange the germs in question, the tech- 
nique at that time permitted only faint glimpses of the real situa- 
tion. Solid culture media with their resulting possibilities for 
quantitative work and the isolation and classification of pure cul- 
tures were as yet undiscovered. It was then necessary to relv 
largely upon microscopic observation of liquid cultures in order to 
determine their purity and it was but natural that the larger motile 
forms should be first recognized. The minute, immotile, lactic 
forms which really made up the bulk of the flora were commonly 
overlooked. 
In the absence of any exact knowledge of the species present it 
was natural that the workers should rely upon general deductions 
from the characteristics of groups of forms. Thus the analogy 
between the breaking down of the casein in cheese and the changes 
observed in milk cultures of enzym-forming bacteria led Duclaux 
to suggest that these forms were the cause of cheese ripening. In 
his opinion, the constant presence of such forms 1 in cheese rendered 
the causal relation practically certain. 
It should be remembered that Duclaux worked with the semi- 
soft cantal cheese while the later studies have been made on en- 
tirely different kinds representing for the most part the various types 


*Duclaux, E. Ann. agron., 1878-1882, also Le lait, Etudes chimiques et 
micrcbiologiques. Paris. Bailliére. 1807. 
