ASIATIC CHOLERA. 185 



Tenacity of the Cholera- vibrios. The comma-bacilli 

 are endowed with extremely little resistance. They can be 

 destroyed in four minutes in water at a temperature of 52 

 C. (125.6 F.). Lower temperatures are, however, better 

 borne, although the bacilli die in ice after the lapse of a 

 few days. The susceptibility of comma-bacilli to small 

 amounts of acids has already been mentioned. The ad- 

 dition of not more than 0.07 or 0.08 per cent, of hydro- 

 chloric or nitric acid to neutral culture-media is capable of 

 preventing all development. These facts explain why the 

 normal gastric juice, with its hydrochloric-acid content of 

 about 0.2 per cent, constitutes an insurmountable obstacle 

 to the cholera-vibrios. If cholera-bacilli are spread in a 

 thin layer upon a basis of any sort so that they are ren- 

 dered completely adherent and dry, they lose their capa- 

 bility of development in the course of three hours. Dried 

 upon the hand, they survive only for one or two hours. 

 The same rapid destruction (in any event within twenty -four 

 hours) takes place in connection with the contamination of 

 smooth surfaces such as floors, paper, etc. with comma- 

 bacilli. From these considerations it may be concluded 

 that the transmission of cholera by way of the air, through 

 the intermediation of dried particles of dust, is scarcely 

 possible. Surrounded by moisture the comma-bacilli may, 

 under favorable conditions, retain their vitality for a long 

 time, up to nine months as, for instance, in moist linen 

 rolled together compactly and kept in a cool place, and 

 containing the vibrios in pure culture, so that they are not 

 overgrown by other bacteria. They may be found alive in 

 agar-cultures and gelatin-cultures after the lapse of six 

 months. The usual antiseptics, even in feeble concentration, 

 destroy the cholera -vibrios within a short time : one-half per 

 cent, carbolic acid, for instance, in the course of a few 

 minutes. In fresh milk the comma-bacilli retain their 

 vitality for twenty-four hours ; in boiled milk, for two or 

 three days ; upon articles of food protected from evapora- 

 tion under a glass jar, for from four to eight days. The 

 bacilli sometimes survive for weeks in the dejections of 

 cholera-patients, although this occurs only under peculiarly 

 favorable conditions. In sterilized water, from whatever 

 source, living cholera-vibrios can be demonstrated after the 

 lapse of months. In unsterilized water, on the other hand, 

 and especially in bacterial mixtures, in which the comma- 



