20 



CLINICAL BACTERIOLOGY. 



certain amount of rotation. It is most marked in quite 

 young cultures, but is in greater degree dependent upon the 

 variety of bacterium, the culture-medium, and the tempera- 

 ture. Many species of bacteria possess spontaneous move- 

 ment throughout their whole life ; others only during 

 certain phases, losing it, for instance, preceding spore- 

 formation. 



The multiplication of bacteria takes place usually by 

 means of fission in pairs. The time in which this division 

 occurs varies for different varieties. In the case of some 

 species, if all of the extrinsic conditions (culture-medium, 





Fig. 5. Bacteria showing flagella : i, Bacilli of typhoid fever; 2, bacilli coli com- 

 munes ; 3, spirilla of Finkler and Prior; 4, spirilla of Deneke; 5, vibrios of Metschni- 

 koff; 6, spirilla of Asiatic cholera (Nicolle and Morax). 



temperature) are favorable, it is half an hour ; in that of 

 others it is somewhat longer from one to two hours ; while 

 in that of still others, as, for instance, the tubercle-bacillus, 

 it is as much as several days. When the division always 

 takes place in the same direction, and the newly formed in- 

 dividuals remain attached to one another, a chain-like forma- 

 tion results. In the case of rods bacillary filaments result, or 

 pseudofilaments ; the dividing walls between the individual 

 cells of the strand are frequently recognizable with difficulty. 

 In the case of spherules streptococci (chain-cocci) result. (Fig. 

 6.) The bacteria may, however, after division be arranged, 



