HISTORY OF OUR KNOWLEDGE OF BACTERIA. 1 05 



Infusoria; but the year 1853 marked the com- 

 mencement of a new era in their history, for Robin 

 then pointed out the affinity of the Bacteria and 

 Vibrios to Leptothrix. Davaine, in 1859, still 

 more definitely insisted that the Vibrios were 

 vegetables, and that they were in fact allied to 

 the Algcc. 



Since that time a flood of light has poured in 

 upon the subject through the writings of Hoff- 

 mann, Pasteur, Cohn, Rabenhorst, Hallier, Billroth, 

 Warming, Nageli, Magnin, Marchand, Sternberg, 

 Van Tieghem, Lister, Klein, Koch, Fliigge, De 

 Bary, Zopf, Cornil, Babes, and many other workers 

 in the recent widespread revival of bacteriological 

 research. 



Of all these writers we are most indebted to 

 Cohn,* not only on account of his researches, which 

 extended over very many years, but also for his 

 system of classification, which has since been 

 almost universally adopted. 



In his first classification, published in 1872, Cohn 

 considered the Bacteria as a distinct group be- 

 longing to the Alga, and divisible into four tribes, 

 including six genera : 



I. Sphaerobacteria globules (Micrococcus). 



II. Microbacteria . short rods (Bacterium). 



III. Desmobacteria . long rods (Bacillus and Vibrio). 



IV. Spirobacteria . spirals (Spirochaete and Spirillum). 



* Cohn, Beitrage zur Biologic der Pflanzen, 1872, et seq. 



