CLASSIFICATION OF DAIRY BACTERIA. i 
Potato.—The growth is usually invisible, but sometimes a scanty surface film 
may be seen. 
This streptococcus is very common and in some specimens of soured milk 
comprises ninety-nine per cent. of all the Bacteria present. It has been found 
frequently in the milk in Middletown, in storrs,in New York City, and else- 
where. Where it occurs it is commonly the cause of the souring of milk, but it 
is not so common as the elongated form which we have classified as Bact. lactis 
acid. 
The white cocci that produce acéd but no slime are very numerous and their 
separation into groups is uncertain. We have divided them into six groups, 
but the distinctions between them are not satisfactory. Each of the groups has 
slight variations and it may be that some of them would be better united 
together. For the present, however, we recognize the following, dividing them 
first according to their action on various sugars, and secondly by the abundance 
of surface growth produced on media. 
S. lacticus J. The essential character of this type is the production of acidity 
in dextrose but not in other sugars. 
Morphology.—A streptococcus in pairs or short chains. Size, .6u-1.24. The 
Gram stain is positive. 
Gelatine colony.—This is not characteristic. It is round, white to yellowish 
and spreads over the surface, forming a colony I mm. in diameter. 
Gelatine stab.—A needle growth and a surface growth. 
Agar streak.—Moderately abundant, white. 
Fermentation tubes.—Dextrose bouillon is rendered acid, but no gas is pro- 
duced and no acidity in other bouillons. 
Bouillon.—A sediment and turbidity and sometimes a pellicle. 
Milk.—Becomes acid, but is not curdled, and no other change is noticed. 
Potato.—Growth very slight or wanting. 
Four cultures of this group have been studied—two derived from milk fresh 
from the udder, one from the dust of the stable, and one from cheese. They 
differ slightly, as follows: 
Variety A.—This culture, from the udder, produces no turbidity, but a slight 
pellicle in bouillon. 
Variety B.—From the udder. Produces turbidity and no pellicle in bouillon 
and does not make milk acid. 
Variety C.—From stable dust. Has a negative Gram stain, a turbidity and 
a pellicle in bouillon, and milk is not acid. 
Variety D.—¥rom cheese. Shows a turbidity and a pellicle in bouillon; 
milk is acid, and there is a luxuriant potato growth. 
S. lacticus [/,—Vhis produces acid in lactose and saccharose but not in 
dextrose. Its other points of difference are as follows: Gram stain is nega- 
tive; the gelatine colony is very small and transparent; no pellicle is ever 
formed on bouillon; there is no action on milk and there is an abundant potato 
growth. 
