CHAPTER XVII. 



BACTERIACEAE. 



GENUS BACTERIUM AND ITS SPECIES PATHOGENIC FOR 

 ANIMALS. 



General discussion of the genus Bacterium. In Migula's: 

 classification the genus bacterium includes all the non-motile 

 rod-shaped bacteria. The genus is based morphologically on 

 the absence of organs of locomotion, or flagella. In some of 

 the earlier classifications, the genus Bacterium was based on 

 the absence of spores and many non-motile, spore-bearing, rod- 

 shaped bacteria were called bacilli. Several of the more com- 

 mon pathogenic organisms such as Bacterium anthracis, Bac- 

 terium mallei and others belonging to this genus were de- 

 scribed according to the older classifications as belonging to 

 the genus Bacillus. The genus Bacterium as defined by~ 

 Migula contains a large number of the more important patho/- 

 genie species. 



History. The genus Bacterium was introduced by 

 Ehrenberg 1 in 1828. In the different classifications of bac- 

 teria since his time it has been used with different meanings. 

 In the more recent systems the sense in which the term is used 

 is quite different. Lehmann and Neumann apply the name- 

 bacterium to all rod-shaped bacteria in which spores are un- 

 known. Migula 2 uses the term bacterium for all non-motile 

 rods, disregarding the production of spores. Fischer does not 

 use this genus in his classification. 



As already stated, Migula's system seems to lend itself to 

 the classification of pathogenic bacteria much better than 

 others for the reason that it has less genera and consequently 

 changes the generic names of a smaller number of species. 



1 Ehrenberg. Abhandlungen der Akademie der Wissenschaften v 

 1829, p. 15. 



2 Migula, loc cit. 



