576 BACTERIOLOGY. 



tion. In these they occurred only in involution 

 forms. 



The comma bacillus is killed by exposure to moist 

 heat at 60 C. in ten minutes. The bacilli have been 

 found alive in ice kept for a few days, but ice which 

 has been preserved for several weeks does not contain 

 living bacilli. 



Chemical disinfectants readily destroy the vital- 

 ity of cholera vibrios. For disinfection on a small 

 scale, as for washing the hands when contaminated with 

 cholera infection, a 0. 1 per cent, solution of bichloride 

 of mercury or a 2 to 3 per cent, solution of carbolic acid 

 may be used. For disinfection on a large scale, as for 

 the disinfection of cholera stools, strongly alkaline milk 

 of lime, according to PfuhFs experiments, is an excel- 

 lent agent. The wash of cholera patients, contaminated 

 furniture, floors, etc., may be disinfected by a solution 

 of 5 per cent, carbolic acid and soap-water. The dis- 

 infecting action of mineral acids, particularly of sul- 

 phuric acid, has been advantageously employed for the 

 disinfection of entire systems of water-works into which 

 cholera bacilli had gained access. 



Pohl, Bujivid, and Dunham have shown that when 

 a small quantity of chemically pure sulphuric acid is 

 added to a twenty-four-hour bouillon culture of the 

 cholera bacillus containing peptone a reddish-violet 

 color is produced. Brieger separated the pigment 

 formed in this reaction the so-called cholera-red and 

 showed that it was indol, and that the reaction was 

 nothing more than the well-known indol reaction. Sal- 

 kowski and Petri then demonstrated that the cholera 

 bacilli produced in thin bouillon cultures, along with 

 indol, nitrites by reduction from the nitrates con- 



