8CHIZOMYCETE8. 



(a) Cohn separated Bacteria into four tribes, as follows : 



(1) Spharobacteria, with spherical cells. The only genus is Micrococ- 

 cus. The species M. crepusculum, M. candidus, and M. urece produce 

 certain kinds of fermentation ; the color-producing species are M. pro- 

 digiosus (a, Fig. 145), which causes the blood-like patches on -bread, 

 flour, paste, etc., M. luteus, M. aurantiacus, M. chlorinu*, M. cyaneus, 

 and M. violaceus ; those producing or accompanying diseases are M. 

 vaccince, M. diphthericus, M. septicus, and M. bonibycis. This latter 

 group is of great importance, but it is one the investigation of which 

 presents unusual difficulties. Oth- 

 er species than those named are 



supposed to exist. 



(2) Microbacteria, with very 

 small cylindrical cells. The only 

 genus is Bacterium. The species 

 are, B. Termo (b, Fig. 145), the 

 common agent of putrefaction ; 

 B. lineola (c. Fig. 145), a larger 

 species found in brooks and 

 ponds ; B. xanthinum and B. syn- 

 cyanum, which are color-produc- 

 ing ; and B. ceruginosum, which 

 is found in blue-green pus. 



(3) Desmobacteria, with filiform 

 cells. There are two genera, Ba- 

 cillus, with the filament straight, 

 and Vibrio, with the filament curv- 

 ed or undulated. Of the first there 

 are three species, viz.: B. subtilis, 

 which is the butyric ferment ; B. 

 ulna (d, Fig. 145), much like the 

 preceding, but larger ; and B. 

 anthracis, which is the cause or 

 accompaniment of the diseases 



lignant pustule." VArio has two 3p^' Mutant." x'65o!-After Cohn. 

 species, viz. : V. Rugula (e, Fig. 145), whose cells are thick and rather 

 short ; and V. serpens, whose cells are of smaller diameter, but of 

 greater length than the preceding. 



(4) Spirobacteria, with spirally twisted cells. There are two genera, 

 SpirochcBte, with a much twisted spiral ; and Spirillum, with a lesa 

 twisted spiral. Of the first the single species is Sp. plicatilis (f, Fig. 

 145), and of the second, Sp. temie, Sp. andula and Sp. volutans (g, 

 Fig 145), the latter a gigantic species, with a flagellum at each end 

 of the spiral. 



(6) Bacteria may be readily procured for study by infusing a pinch 



Fig. 146. a, Micrococcits prodigiosus, 

 (Monas prodigiosus of Ehrenberg) ; b. 

 Bacterium Termo, zoogloea stage ; c, Bac- 

 terium lineola : d. Bacillus ulna ; e, Vi- 

 ma- brio Rugula ; f, Spirochcete plicatilis ; ff, 



