574 BACTERIOLOGY. 



simple peptone solution, and it has been shown by ex- 

 periment that it also multiplies to some extent in steril- 

 ized river or well-water, and preserves its vitality in 

 such water for several weeks or even months. Koch 

 found in his early investigations that rapid multiplica- 

 tion may occur upon the surface of moist linen, and also 

 demonstrated the presence of this spirillum in the foul 

 water of a tank in India which was used by the natives 

 for drinking purposes. 



The comma bacillus belongs to the class of aerobic 

 organisms, inasmuch as it grows readily only in the pres- 

 ence of oxygen, and that it develops active motility 

 only when a certain amount of oxygen is present. It 

 does not grow in the total absence of oxygen, but a 

 small quantity of oxygen is all that is required for its 

 development, as in the intestines. 



Temperature is also of considerable importance in the 

 growth of cultures. Active growth does not begin 

 until a temperature of 22 to 25 C. is reached, though 

 the optimum growth is between 30 and 40 C. 



The vitality of cultures of the comma bacillus is 

 quickly destroyed by desiccation. If a culture be 

 spread on a cover-glass and exposed to the action of 

 the air at room-temperature the bacilli are dead at the 

 end of two or three hours, unless the layer of culture 

 is very thick, when it may take twenty-four hours or 

 more to kill all the bacilli. This fact indicates that 

 infection is not produced by means of dust or other dried 

 objects contaminated with cholera bacilli. The trans- 

 misson of these organisms through the air, therefore, 

 can only take place for short distances, as by a spray of 

 infectious liquids by mechanical means as, for instance, 



