6 BACTERIOLOGY FOR NURSES 



Three terms are in use to designate the spirilla, i.e., vibrio, 

 spirillum, and spirochete. According to Migula the names are 

 made to indicate the possession and arrangement of flagella. 

 Fliige, another systematist, applies the term " vibrio " to all forms 

 that are slightly curved, and " spirillum " and " spirochete " to 

 all wavy forms. The classification of this group is at present an 

 open question. 



Size. In size bacteria vary greatly. The cocci range from l 



0.5/* ( r nnnn inch) to 2/* ( inch) in diameter. The small- 



oOuuu 



est bacillus known, the influenza bacillus, has an average size 

 of 1/*X0.2/*. The largest bacillus recorded (B. Biitschlii) is 50^ 

 to GO/* long and 4^ to 5/t wide. 



Reproduction. One of the most characteristic features of 

 bacteria is their method of reproduction. They multiply by 

 simple division or fission (hence the term Schizomycetes or fission 

 fungi). This method of multiplication is the distinguishing 

 feature which separates bacteria from yeast, the latter plants 

 multiplying by a process known as budding. When a bacterial 

 cell is about to divide a constriction appears j^ thp-miflfjj*' which 

 gradually becomes more pronounced until the cell is completely 

 divided and two individuals can be recognized. These may be- 

 come detached at once, or, owing to the slimy envelope which is 

 more or less developed in all bacteria, may remain attached. 



Certain cocci divide as described into two individuals which 

 separate at once (micrococci) ; others dividing in one plane remain 

 attached in pairs (diplococci), or in shorter or longer chains 

 (streptococci) ; others, dividing in two directions, one at right 

 angles to the other, form groups of four (tetrads) ; others divide 

 in three directions and form packets in cubes of eight (sarcinse) ; 

 others again divide in any axis and form irregular grape-like 

 bunches (staphylococci) . 



Division among the bacilli and spirilla always takes place at 

 right angles to the long axis of the cell. The cells of the bacilli 



1 1/* = 1 micron or micromillimetre = mm., about ' OKnnn inch. 



1 (MX) 



