CHAPTER IX. 



CLASSIFICATION OF THE BACTERIA. 



66. First Attempt by 0. F. Muller. 



IT has already been mentioned in the Introduction ( 2) that Leeuwenhoek 

 observed bacteria as far back as the end of the seventeenth century. For a long 

 time, however, nothing more was done than merely to admire the appearance 

 presented by these organisms under the microscope ; and since many of them 

 were observed to exhibit brisk movements, they were considered as animals and 

 denominated animalcule*. 



The first to study these organisms from a scientific standpoint, and to 

 arrange and systematise the multitude of forms, some of which were already 

 known, while others were discovered and described by himself, was the Danish 

 investigator Otto Friedrich Muller of Copenhagen. In his important work 

 "Animalcula infusoria fluviatilia et marina," published in 1786, all the small 

 animals unsuitable for inclusion in Linna?us's sixth class, Vermes, were classed by 

 him under the name of Infusoria (infusion animalcule), and he divided these 

 into two main groups : those provided with external organs and those devoid 

 of same. He also originated the generic names Vibrio, Monas, and Proteus, 

 still in use. 



The next worker to whom we are indebted for important conclusions respect- 

 ing the character and species of bacteria is Christian G. Ehrenberg. In his 

 work " Die Infusionstierchen als vollkommene Organismen " (The Infusoria as 

 Perfect Organisms), published in 1838, the generic names Bacterium, Spirockcete, 

 and Spirillum first occur. He also classed all these organisms with the animal 

 kingdom, by reason of their (frequently very active) spontaneous motion. 



It was left to the Breslau botanist FERDINAND COHN (V.) to ascertain, in 

 1853, that the organisms we now know as bacteria are of a vegetable nature. 

 This he established by proving the lack of animal organisation, and also from 

 the fact that these creatures increase by subdivision after the manner of the 

 algse, from which they differ, as he says, merely in one characteristic : the 

 absence of chlorophyll. Four years later NAGELI (V.) bestowed on these 

 organisms the name of Schizomycetes, which they still retain. 



67. Cohn's Classification. 



The first point was to bring the confusion of forms into order. What 

 characteristic should be taken as a guide thereto? Were there several at 

 disposal on which one could rely? These questions COHN (I.) may well have 

 asked himself when, in 1872, he felt himself impelled to attempt a classification 

 of the bacteria, and finally thought his object attained by the following 

 system : 



I. Sphcerobacteria, globule bacteria 

 Genus I : Micrococcus. 



II. Microbacteria, short rod bacteria. 

 Genus 2 : Bacterium. 

 69 



