Mar. 25, 1914 
495 
Streptococci in Milk 
of characters can be adopted for all classes of bacteria. The significant 
characters will be found for each group only by a study of its normal 
activities and the utilization of those functions which show the nature, 
limitations, and relationship of the group. The striking characteristic 
of the streptococci is their ability to form acids from carbohydrates and 
related substances, and this peculiarity has been very generally utilized 
for purposes of classification. The voluminous literature bearing pro 
and con on the constancy and the value of these tests has been reviewed 
fully in various papers and need not be taken up here. It may be safely 
asserted, however, that the fermentative ability is as constant and as 
significant for purposes of classification as the characters adopted by 
those who reject the fermentation tests as too variable. For instance, 
Davis, who rejects the sugar fermentations as untrustworthy, divides the 
C08 o ^ D 
C D U E F 
O 
CD 
a 
H 
Fig. 2.—'Types of cells of streptococci. 
streptococci into five groups on the basis of hemolysis, green colonies on 
blood agar, capsule, solubility in bile, inulin fermentation, experimental 
arthritis, and experimental endocarditis. 1 
For purposes of classification, we have used the liquefaction of gelatin 
and the fermentation of dextrose, saccharose, lactose, raflinose, starch, 
inulin, mannite, and glycerin. Adonite and dulcite were tested, but as 
they were fermented by only one or two of these cultures they were of 
no value. The liquefaction of gelatin was determined by inoculating 
the surface of the gelatin tube with a few drops of a broth culture and 
measuring the liquefaction after 30 days at 20° C. 
The fermentation of the test substances was determined in a medium 
made as follows: 
Per cent. 
Beef extract. o. 4 
Peptone. 1. o 
Dibasic potassium phosphate.5 
Test substance. 2.0 
1 Davis, D. J. Interrelations in the streptococcus group with special reference to anaphylactic reactions. 
Jour. Infect, Diseases, v. 12, no. 3, p. 386. 1913. 
28736 0 —14-s 
