CHOLERA SPIRILLUM 255 



culture which has been incubated twenty-four to forty-eight 

 hours. When the growth is that of a cholera spirillum a reddish 

 pink color appears, the so-called " cholera red reaction." 



Resistance. The cholera spirillum has much the same degree 

 of resistance that other spore-free organisms possess. It is killed 

 by exposure to moist heat at 60 C. in ten minutes and at 100 C. 

 in one minute. Chemical disinfectants are speedily effective. 

 The organisms are especially sensitive to drying, hence it is unlikely 

 they are ever carried in a living condition in the dust particles 

 in the air. In the dejecta of cholera patients they remain alive 

 usually from one to three days, although occasionally they have 

 been found after a much longer period. In running water they 

 persist for six or seven days, and in stagnant water for about eigh- 

 teen days. In milk the acidity produced by other bacteria soon 

 destroys them. 



Modes of Transmission. Cholera spirilla leave the body of 

 infected patients in the feces and so far as is known enter only by 

 way of the mouth. Consequently, food and water, directly or in- 

 directly contaminated with the dejecta of infected individuals, 

 are the main cause of the spread of the disease. Water is probably 

 solely responsible for the great epidemic outbursts. 



The earliest authentic account of an epidemic of cholera trace- 

 able to polluted water is the Broad Street pump case in London 

 in 1854. Within five weeks 616 deaths occurred in the vicinity 

 amongst people who drank of the water. The outbreak happened 

 before the days of bacteriology, consequently absolute proof of 

 the presence of the cholera spirillum was not available. Inspection 

 of the premises, however, revealed a cesspool with defective brick- 

 work from which fluid material was constantly percolating into 

 the well. 



In Hamburg in 1892 a similar explosive outbreak occurred. 

 Cholera was taken to the city by immigrants and the water of the 

 Elbe was infected with their discharges. The sewers of Hamburg 

 emptied into the river near the water intake from which the city 

 received its supply for drinking purposes. The adjoining city of 

 Altona received its water from the same source, but purified it by 



