
aft, 
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CLASSIFICATION OF DAIRY BACTERIA. 185 
Varveties C.and D, These two differ from common aerogenes bacteria in 
making mzlk bitter. They also show some other rather peculiar characters, al- 
though they plainly belong to the acrogenes type. Variety C was isolated by 
ourselves from milk in Connecticut and differs from the type in the following 
points: the litmus gelatine is not acid; a brown fluorescence is produced on 
agar; dextrose is acid, but no gas is produced; milk is curdled at 37° only, and 
is very bitter; potato growth is very luxuriant, white, and the potato is dis- 
colored. 
Variety D, sent us by Harding, produces gas in dextrose only, but all three 
sugar bouillons become slimy; there is no closed arm growth, no pellicle on 
bouillon; milk bitter; potato growth is luxuriant and the potato is discolored. 
THE COLI COMMUNIS TYPE. 
The rest of the gas producers found in milk are flagellates. Among them 
we recognize some with thick colonies, like aerogenes, and others with thinner, 
spreading colonies, of the col type. In most cases the flagella are peritrichic, 
but there is one type found by us several times that is monotrichic. Beginning 
first with the types most similar to aerogenes, we recognize the following 
varieties: 
B. colt aerogenes n. s. 
Morphology.—Size, 1u-3u x Iu-1.4mu. There are no chains nor spores; Gram 
. Stain is negative, and the bacilli are peritrichic. 
Gelatine colony.—Prominent, thick, moist, smooth, large, surface colonies. 
Gelatine stab.—A needle growth, and a thick, white surface growth. 
. Agar streak.—Filiform, raised, smooth, opaque, cream-white to brown. 
fermentation tubes.—All three sugars are rendered acid, gas is produced, and 
there is growth in the closed arm. The amount of gas is not very great. 
Bourlion.—A sediment and turbidity, and usually a pellicle. 
Milk.—Rendered strongly acid and curdled with gas bubbles. 
Potato.— White to straw color, luxuriant. 
Grows at both 20° and 37°, better at 37. Aerobic. Indol is produced. 
Some twenty of Harrison’s organisms would belong here. They differ among 
themselves very much in their gelatine colonies, and somewhat in their growth 
onagar. There are also differences in their powers of fermenting different 
sugars. We do not see in these points any good reasons for separating them. 
One variety, however, may be properly recognized in accordance with the plan 
adopted above. 
Variety A.—Produces no indol. 
Here apparently belongs B. Schaffext. 
B. coli communis (Esch.) This differs from the last chiefly in producing a 
thinner colony on gelatine, which is umbonate, and has a granular, lobate edge. 
Its agar growth is smooth and white. Upon potato it does not usually grow 
luxuriantly, and indol is produced. 
