54 



PHARMACEUTICAL BACTERIOLOGY 



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

 lus moves at the rate of i8 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 6 have fixed bodies, motion 

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



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. 



