CLASSIFICATION OF THE BACTEEIA. 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 Desmobaeteria, 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 desmobaeteria comprehend the g. Bacillus 

 and Vibrio ; the first established by Cohn for the 

 rectilinear filaments is composed of the B. subiilis, 

 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. 



