CLASSIFICATION OF DAIRY BACTERIA. 135 
Fermentation tubes.—All three sugar bouillons are rendered acid and there is’ 
commonly a closed arm growth, but never any gas. 
Bouillon.—F requently there is no sign of growth, but there is commonly a 
slight sediment. 
Milk,—Milk is rendered strongly acid and promptly curdled in from six hours 
to two days. The curd is smooth and hard, without gas bubbles, and never 
shows any digestion. 
Potato,—Usually no growth, but sometimes a thin, transparent film. 
Grows at 20° and 37°, but better at 20°. Facultative anaerobic, growing 
better without oxygen, and hence curdling milk at the bottom first. 
The most characteristic features of this organism are the peculiar Z¢mus- 
gelatine colonies, the absence of surface growth, and the smooth, hard, acid curd 
in milk. 
Variety A.—This differs from the common type simply in its extremely 
minute colony, which is invisible to the naked eye, is merely transparent and 
does not show the characteristic spines. In our previous list this was called 
No. 202, but we now think that it is only a less robust form of the type. In all 
other respects the two agree perfectly. The difference of the colonies on gela- 
tine, however, is usually very striking, that of the variety A being not more 
than I-10 the size of the type. It is less frequently found, also, than that of the 
type. 
Both the type and variety A show great variability in their acid-producing 
power. Sometimes they curdle milk in as short a time as six hours (at 37°), 
other cultures in twenty-four hours, others, again, in two or three days, and 
finally, some, identical in other respects, fail to curdle it at all, although they 
make it strongly acid. These variations in acid-producing power do not seem 
to us to be sufficient to warrant us in recognizing them even as varieties. They 
are certainly subject to modification in the same cultures. Cultivation in milk 
noticeably increases this power. Cultures, when first isolated, show « weak 
growth and a weak curdling power, but after a few days’ growth in milk this 
power is very greatly increased. A gelatine plate made from fresh milk shows 
weak colonies, growing slowly, with a weak acid production. A plate made 
from the same milk after two days shows not only more numerous colonies but 
colonies much larger, more acid, and growing much faster. It appears thus that 
this organism adapts itself to milk, which seems to be its most favorite medium 
for growth. : , 
This is the organism which, in previous papers (Annual Rep. Storrs Exp. 
Sta., 1901), we have shown to outgrow all other bacteria in milk at 20°, and com- 
monly to comprise 99% or more of the bacteria in milk kept at 20°. We have 
found this organism all over the United States from the Pacific to the Atlantic, 
and it has been sent to us from Europe as one of the most common lactic bac- 
teria there. It is present in practically every cheese which we have studied, 
including both hard and soft cheeses. It has been many times studied and 
been given very many different names. It appears to be the same organism 
which has received the following names by different authors; Lactic bacterium 
of Kozai, Lactic bacterium of Utz, Strept. acidi lactici of Marpmann, Bact. lactis 
acidi Leichmann, B. Jactis acidi Giinther and Thierfelder, B. actdi paralactis a 
of Freudenreich (also several others of his cultures are nearly identical), Bac¢ddas 
