22 THE BACTERIA. 



cese, with several families with which the different 

 genera of bacteria have many affinities. He rec- 

 ognized, however, that the absence of chlorophyll 

 approaches them, at least from a functional point 

 of view, to the fungi. Upon this point we may 

 say that for other botanists this character is de- 

 cisive, and the bacteria are classed as fungi. 



M. N'ageli, who takes this view, describes them 

 under the name of Schizomycetes. Cohn divides 

 the bacteria into four tribes, comprising six 

 genera : 



1. The Sphcerobacteria or globular B. 



2. The Microbacteria or rod B. 



3. The Desmobacteria or filamentous B. 



4. The Spirobacteria or Spiral B. 



We will return to this classification. 



In 1874, M. Th. Billroth, in his researches upon 

 the Coccobacteria septica, expressed opinions en- 

 tirely different from those of Cohn. According 

 to Billroth, the bacteria differ considerably in 

 form according to the medium in which they are 

 placed and divers circumstances. He claims that 

 they constitute but a single species, the C'occobac- 

 teria septica. This vegetable organism can pre- 

 sent itself under the form of globular articles 

 (coccos) or under that of rods (bacterie). These 

 two forms may reproduce themselves by becoming 

 elongated and dividing transversely, or may pass 

 the one into the other. Billroth claims to have 

 found both forms united in a single filament, a 



