THE ORIGIN OF SOME OF THE STREPTOCOCCI FOUND 
IN MILK 
By L. A. Rogers and Arnold O. Dahlbbrg, 
Dairy Division , Bureau of Animal Industry 
INTRODUCTION 
In the higher plants and animals we are accustomed to associating 
species with a more or less definite habitat. Certain animals are found 
only in certain localities. One species of trees may be found only on 
a particular type of soil. A still narrower limit of distribution is found 
in some of the parasitic fungi which grow only on closely related host 
plants. Zoologists or botanists find the types on which they base their 
descriptions in the natural habitat of the organism. This relation has 
not always existed in the published descriptions of bacteria. The 
association of a natural group with a particular habitat has been more 
or less incidental, except perhaps with the pathogenic bacteria, and 
even with some of these it is not impossible that the pathological con¬ 
ditions under which they are found may not be the true habitat of the 
species. The colon group, while it is frequently found in water and milk, 
has its natural habitat in the intestinal tract of warm-blooded animals. 
Winslow found that certain chromogenic cocci were associated with 
the skin of animals. 1 Some of the English bacteriologists have pointed 
out that the streptococci from horse manure, for instance, have a set of 
physiological reactions which differentiates them from those from saliva 
or pathological conditions. 3 It is only through a knowledge of the habitat 
and the study of sufficient cultures to establish a type that true bacterial 
species can be determined. If we were to write a description of the 
German people we would go to Germany, not to an American city 
where German immigrants live. 
Countless descriptions have been written of bacteria isolated from 
mi lk until we have come to consider certain types as peculiar to this 
medium. The bacteria found in milk, however, are a heterogeneous 
collection, and the true types of milk bacteria are to be sought in the 
sources from which milk is contaminated. Esten has suggested that 
the streptococci or lactic-acid bacteria of milk come originally from 
the mouth of the cow. 8 The feces of the animal must, unfortunately, 
1 Winslow, C. E. A., and Winslow, Anne R. Systematic relationships of the Coccacese. ed. i, 300 p., 
iUus. New York, 1908. 
* Andrewes, F. W. Report on the micro-organisms present in sewer air and in the air of drains. 36th 
Ann. Rpt. Local Govt. Bd. [Gt. Brit.], 1906-07, Suppl. Rpt. Med. Off., p. 183-204. 1908. 
8 Esten, W. M. Bacterium lactis acidi and its sources. Conn, Storrs Agr. Expt. Sta. Bui. 59, 27 p., 
5 fig. 1909. 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
Vol. I, No. 6 
Mar. 2 s, 1914 
