CLASSIFICATION OF THE BACTERIA 25 



example, there is one tj'pe of rod-shaped organism which 

 produces typhoid fever, another type somewhat closely 

 related to it which causes dysentery. These two species are 

 brought together in the genus Bacterium. This genus, 

 with several other genera of bacteria, are united into the 

 family Bacteriaceae, and this family again united with 

 others to form the order Eiihacteriales. 



The rules which govern the giving of scientific names to 

 plants and animals should be recognized also in bacteriology. 

 To every kind of organism a name should be given con- 

 sisting of two words: the first of these a proper name, al- 

 waj's capitalized, the name of the genus; the second name 

 is the name of the species. This latter name is never capi- 

 talized unless it is derived from a proper noun. All genus 

 and species names are in Latin. The name of the organism 

 which causes typhoid fever is Bacterium typhosum. Fre- 

 quently the name of the man who first described the organ- 

 ism under the particular name accepted is given also, thus, 

 Bacterium coli Escherich, indicates that Escherich first ap- 

 plied this name to the organism called the colon bacillus. 

 Sometimes investigators have named species but have placed 

 them in the wrong genus. The man who first recognized 

 the species may have his name written in parentheses be- 

 tween the name of the species and the name of the individ- 

 ual who first used the right combination, for example, an 

 organism sometimes associated with pus production in 

 animals is Pseudomonas aeruginosa (Schroeter) Migula. 

 This indicates that Schroeter first used the name aeruginosa 

 but that Migula placed this species in the genus Pseudo- 

 monas. 



The species name of an organism should ordinarily con- 

 sist of a single word. Some bacteriologists have not fol- 

 lowed this rule and have given complex Latin names to 

 organisms on the theory that a name should be a descrip- 

 tion, for example, one species was termed Bacillus saccharo- 



