8CHIZ0MYCETES. 



313 



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

 (1) Sphmrdbaeteria, with spherical cells. The only genus la Micrococ- 

 cus. The species M. crepusculum, if. eandidus, and M. urem 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. clilorinus, M. cyaneus, 

 &nA M. violaceus ; those producing or accompanying diseases are M. 

 vaccime, M. diphthericus, M. septieus, and M. iomhycis. 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. 



(3) Micrdbacteria, 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 (e. Fig. 145), a larger 

 species found in brooks and 

 ponds ; B. xantltinum 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.: J}, sublili.i, 

 which is the butyric ferment ; B. 

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

 preceding, but larger ; and B. 

 anthracis, which is the cause or 

 accompaniment of the diseases 

 known as nitlhrnx and "ma- 

 lignant pustule." Vibrio has two 

 species, viz, : V. Eugufa {e, Fig. 145), whose cells are thick and ratlier 

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

 greater length than the preceding. 



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

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

 twisted spiral. Of the first the single species is 8p. plieatilis (/, Fisr. 

 145), and of the second, Sp. tenue, Sp. andula and 8p. volulans (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 hj infusing a pinob 



145. a. Mfcrococcus prodigiosue, 

 [Monas prodigiosus of Ehronberg) ; 6, 

 Bacterium. Ternio, zooglcea stiige ; a, BaC' 

 teHum lineola : d. Bacillus ulna ; e, Yi- 

 brio Bugula ; f, SpiroclKsUplicaiilis ; g. 

 Spirillum wlutans. X 650. — After Cohh. 



