398 BACTERIA PATHOGENIC TO MAN 



days, and in an aquarium containing plants and fishes, the water of 

 which was inoculated with cholera germs, they were isolated several 

 months later from the mud at the bottom. In running river-water, 

 however, they have not been observed for over six to eight days. For 

 the cholera organisms the conditions favorable to growth are a warm 

 temperature, moisture, a good supply of oxygen, and a considerable 

 proportion of organic material. These conditions are fully met with 

 outside the body in but very few localities. 



The comma bacillus has the average resistance of spore-free bac- 

 teria, and is killed by exposure to moist heat at 60 C. in ten minutes, 

 at 95 to 100 C. in one minute. The bacilli have been found alive 

 kept for a few days in ice, but ice which has been preserved for several 

 weeks does not contain living bacilli. 



Chemical disinfectants readily destroy the vitality of cholera vibrios. 

 For disinfection on a small scale, as for washing the hands when con- 

 taminated 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 is an excellent 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 Spread of Cholera. Cholera is practically always transmitted 

 by means of water or food contaminated by the spirilla, and there is 

 no doubt that the contamination is in most all cases through the direct 

 soiling of the water by the feces of cholera patients. Flies which have 

 fed or lighted on the discharges of cholera patients or on things con- 

 taminated by them have been found to carry the organisms not only 

 on their feet, but also in their bodies for at least twenty-four hours. 

 Food contaminated by flies is therefore a possible source of infection. 



Pathogenesis. None of the lower animals is naturally subject to 

 cholera, nor has any contracted the disease as the result of the ingestion 

 of food contaminated with choleraic excreta or from the inoculations 

 of pure cultures of the spirillum, either subcutaneously or by the mouth. 

 It has been shown that the comma bacillus is extremely sensitive to 

 the action of acids, and is quickly destroyed by the acid secretions of 

 the stomach of man or the lower animals, when these secretions are 

 normally produced. Nikati and Rietsch produced a choleraic condi- 

 tion in a considerable percentage of dogs, where the virulent cultures 

 were injected directly into the duodenum. Koch sought to produce 

 infection in guinea-pigs per vias naturales by first neutralizing the 

 contents of the stomach with a solution of carbonate of soda 5 c.c. 

 of a 5 per cent, solution injected into the stomach through a pharyngeal 

 catheter and then after a while administered through a similar catheter 

 10 c.c. of a liquid into which had been put one or two drops of a bouillon 

 culture of the comma bacillus. The animal then receives a dose of 1 c.c. 

 of tincture of opium per 200 grams of body-weight, introduced into 

 the abdominal cavity, for the purpose of controlling the peristaltic move- 

 ments. As a result of this treatment the animals are completely nar- 



