54 



PHARMACEUTICAL BACTERIOLOGY 



The rate of motion of bacteria has been measured. The cholera bacil- 

 lus moves at the rate of 18 cm. per hour. The typhoid bacillus is slower 



FIG. 7. General morphology of the Spirillaceae. a, S-shaped or single spiral; b, 

 double spiral; c, multiple spirals; d, slender threads; a and b have fixed bodies, motion 

 being caused by flagellae; c and d, bodies flexible, motion not due to flagellae. 



moving a distance of 4 mm. in one hour. The rate of motion in one and 

 the same species is, however, variable, being comparatively rapid at one 



FIG. 8. Illustrating polymorphism or pleomorphism. Involution forms of the bacillus 

 of Asiatic cholera. (Williams.) 



time under certain conditions of food supply, warmth, etc., and at other 

 times comparatively slow. 



