CLASSIFICATION OF THE BACTERIA, 65 
§ 3.— CLASSIFICATION AND DESCRIPTION OF THE 
GENERA AND SPECIES OF THE BACTERIA. 
We have seen in the historical portion of this 
work, a@ propos of the classifications which have 
been given of the bacteria, that, in 1872, M. Cohn, 
recognizing the numerous relations, absence of 
chlorophyll, mode of nutrition, etc., which make 
these organisms a natural family, divided them 
into four tribes : — 
1. The Spherobacteria, or spherical bacteria. 
2. The Microbacteria, or B. in short rods. 
3. The Desmobacteria, or B. in straight filaments. 
4. The Spirobacteria, or B. in spiral filaments. 
In the spherobacteria, Cohn has only adopted 
one genus, the g. Micrococcus, of which the spe- 
cies are divided into three series, — the pigmen- 
tary M., or chromogenes, the M. of fermentations, 
or zymogenes, and the M. of contagious affections, 
or pathogenes. 
The microbacteria include only the genus Bac- 
terium, with two species, B. termo, Dujardin, and 
B. lineola, Cohn. 
The desmobacteria comprehend the g. Bacillus 
and Vibrio; the first established by Cohn for the 
rectilinear filaments is composed of the B. subtilis, 
Cohn (with B. anthracis as a variety) and the B. 
ulna, Cohn; the second, characterized by undu- 
lating filaments, is reduced to V. rugula and ser- 
pens, Auct. 
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