


CLASSIFICATION OF DAIRY BACTERIA. 53 
Gelatin stab; grows along the needle track as a beaded, tolerably abundant 
growth, but no surface growth. 
Agar and potato; there is no growth whatsoever upon these, nor is there any 
perceptible growth in bouillon. In a fermentation tube containing milk sugar 
bouillon there is no growth even in the closed arm. 
Milk, is curdled in thirty-six hours to four days into a hard homogeneous 
curd, which is strongly acid. There is no separation of whey and no subse- 
quent change. 
This organism, next to the last, is the most common of our dairy species. It 
is found with practical universality in samples of mixed milk, and is present in 
very great numbers in ripened cream. While the number of this organism in 
ripened cream is not as great as in the case of the last species, the proportion is 
always high, and frequently reaches 20% in samples of typical ripened cream. 
This organism and the last comprise in many cases over 95% of the bacteria in 
the normally ripened cream, and they must therefore be regarded as the two 
most important dairy organisms in this region. Metther of them produces the 
typical sour milk odor, such as is developed by No. 208. 
No. 197. &. lactici aerobans, (n. sp.) 
This agrees with No. 202, except that it has no effect on milk, and its growth 
on agar is visible though very scanty. 
Possibly these are the same as Aactl/us a, of Freudenreich. 
No. 41. (Originally found in milk from Uruguay.) 
Morphology; a bacillus, occasionally clinging two together, and on potato 
frequently forming chains. Size, I.1u by .64. When growing in potato it is 
slightly longer than in agar. No spores. 
Temperature; grows best at about 20°-23° C.; at 35° scarcely any growth; 
killed by temperature of 60° C. in ten minutes. 
Gelatin plate; a smooth, round colony under surface. On surface a small, 
grey, raised bead-like colony, spreading somewhat, reaching size of I mm. 
occasionally. Not characteristic. After several years cultivation the gelatin 
colony was found to be always burr shaped, with irregular, more or less radiat- 
ing margins. 
Gelatin stab, slight needle growth. Spreads over surface as a moist, white, 
thick mound, forming a nail growth. Does not liquefy. 
Agar, an abundant, white, smooth, glistening layer, 
Potato, raised, thick, whitish or slightly yellow-tinged layer, differing in 
color with amount of moisture, When very moist, is white, but when dry 
tends to a yellowish tinge. Grows profusely. A pleasant aromatic odor 
developed. 
Milk; does not curdle either at 20° or 35°. After two to three weeks be- 
comes slightly translucent and brownish. The reaction is slightly acid. After 
three to four weeks it seems to digest into a translucent mass. It acquires a 
pleasant aroma, 
This bacterium has been used widely for cream ripening, producing a pure 
flavored butter. , 
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