CONDITIONS OF LIFE , 19 



rods, straight and never spiral ; division in one direction 

 only after elongation of the rods ; and this family has 

 three genera : (a) Bacterium non- flagellated cells, often 

 with endospore formation ; (b) Bacillus cells possessing 

 both lateral and polar flagella, often with endospore forma- 

 tion ; (c) Pseudomonas cells with polar flagella only, 

 rarely endospore formation. The Spirillacese are curved 

 or spiral rods, and include (a) Spirosoma, non-motile 

 forms, (6) Microspira, motile forms with one polar flagellum, 

 (c) Spirillum, motile forms with two or more polar flagella. 

 Various pointed organisms have been described as 

 " fusiform* Bacteria," e.g. in Vincent's angina (see Chap. 

 VIII), but Dobell expresses the opinion that these more 

 probably belong to the Fungi. 



The nomenclature of bacterial species is at present in a chaotic 

 condition. In botanical and zoological nomenclature every species 

 has a binomial name, the first being the generic, the second the 

 specific name. Many bacterial species have received trinomial or 

 multinomial names, which should be inadmissible. The specific 

 name first given to an organism must stand unless it has been used 

 for some other species. 



Conditions of Life of Bacteria 



Bacteria, being living organisms, must be supplied with 

 suitable nutritive substances in order that their life- 

 processes nutrition, reproduction, and the like may be 

 carried on in a normal manner. Being devoid of chloro- 

 phyll they are mainly dependent upon complex organic 

 compounds for the carbon, hydrogen, and nitrogen which 

 enter into their composition, these elements being derived 

 for the most part from proteins and carbohydrates. Some 

 bacteria, however, are able to obtain the requisite nitrogen 

 from such comparatively simple compounds as ammonia, 

 ammonium carbonate, or nitrates, and one group can 

 make direct use of the atmospheric nitrogen. Certain 



