BACIJLLUS CO LI CO MM UN IS. 397

should be important evidence of their separate individ-
uality.

The author has no doubt that the Bacillus coli cotn-
munis is not a single species of bacteria, but is a name
applied to a group whose individual differences are thus
far too similar to enable us to differentiate them. This
opinion seems to be shared by other bacteriologists, some
of whom have attempted to separate the bacillus into
groups, types, or families.

In order to establish a type species of the Bacillus coli
communis, Smith l says:

"I would suggest that those forms be regarded as true
to this species which grow on gelatin in the form of deli-
cate, bluish, or more opaque, whitish expansions with
irregular .margin, which are actively motile when exam-
ined in the hanging drop from young surface-colonies
taken from gelatin plates which coagulate milk within
a few days; grow upon potato, either as a rich-pale "or
brownish-yellow deposit, or merely as a glistening, barely
recognizable layer, and which give a distinct indol reac-
tion. Their behavior in the fermentation-tube must
conform to the following scheme:

^Variety a:

"One per cent, dextrose-bouillon (at 37° C.)- Total
gas approximately *4; HCO2 approximately */L ; reaction
strongly acid.

"One per cent, lactose-bouillon: as in dextrose-bouil-
lon (with slight variations).

"One per cent, saccharose-bouillon; gas-production
slower than the preceding, lasting from seven to four-
teen days. Total gas about %\ HCO2 nearly %. The
final reaction in the bulb may be slightly acid or alkaline,
according to the rate of gas-production.

"Variety $\

" The same in all respects, excepting as to its behavior
in saccharose-bouillon; neither gas nor acids are formed
in it"

1 American Journal of the Medical Sciences, 1895, no, p. 287.