WHAT ARE BACTERIA ? 43 



The genus vibrio consists of spiral filaments which break 

 up into short fragments. 



The spirillum consists of longer filaments that have a 

 helicoid arrangement. 



The spirochsete, of greater length, are spirilla with more 

 numerous turns of the spiral. 



Micrococci, arranged in zooglcea masses and held together 

 by a thick layer of gelatinous material, he called ascococcus ; 

 when held together, but without or with less of this gelatinous 

 material, he gave them the name of punctula. 



Bacteria united by this gelatinous material are called 

 ascobacteria ; without the gelatinous envelope, polybacteria ; 

 bacteria in the form of spiral threads, and massed together, 

 form the myconostoc. 



These bacteria are again divided according to their pro- 

 perties of forming colouring matter, chromogenes ; of setting 

 up fermentation, the zymogenes ; and of giving rise to 

 disease in animals or plants, the pathogenes. 

 'He gave a further classification based on the mode of 

 division of the primary cells : 



1. The bacteria in which the division takes place in one 

 axis only. This includes micrococcus, bacterium, bacillus, 

 leptothrix, crenothrix, cladothrix, vibrio, spirillum, spiro- 

 chsete, ascococcus, punctula, ascobacteria, polybacteria, and 

 myconostoc. 



2. The meristae, in which a membranous thallus divides 

 in two directions but on one plane only, giving rise to the 

 formation of characteristic tetrads. 



3. The sarcinae, in which there is division in three direc- 

 tions, so that the resulting masses always remain cubical in 

 form. 



ZopPs classification rests (Fliigge, "Etiology of Infective 

 Diseases," p. i8o) on the doctrine of pleomorphism, which 

 cannot be accepted as in any way proved except in the case 

 of a few well-known non-pathogenic forms ; but his classifica- 

 tion may be accepted as a basis from which to work in bring- 

 ing proof or disproof of the theory of pleomorphism, al- 

 though it is not at present, at any rate, founded on a large 

 number of facts. 



Zopf, who has studied most carefully the subject of pleo- 

 morphism, holds that several forms may occur in the cycle 



