Cholera vibrios can grow freely in water, especially when it is stagnant and pol- 1 luted with organic matter; and it has been shown that they can live for many days even in bottled water.
The bacilli are destroyed if they are in i free contact with the air while exposed to the sunlight, but the colonies in the interior of the culture-media are aided in their growth, the sunlight serving as I a sort of incubator. When the medium is plentiful, there is more growth than destruction. Virulence is not diminished in those bacteria that show growth. Therefore bacteria in the deeper portions of water are not affected by the solar rays, while those floating on the surface may be destroyed; conclusion drawn that "too much reliance should not be placed on the bactericidal action of sunlight." F. F. Westbrook (Jour. of Path. and Bact., Jan., '96).
As for the action of high or low tem perature upon them, we know that the best temperature for their growth is between 30° and 40° C.; that under 160° C. their growth is checked, but their vitality is preserved, even if zero or below zero is reached; they have been found to resist a temperature of —31.8° C. (24° F.), so that it may be supposed that the germs may survive an entire severe winter. On the contrary, they are killed after some days by a temperature of 50° C., and in a shorter time by a tempera ture of 75° C. Direct sunlight dimin ishes, but does not destroy, their vitality and virulence.
A distinct degree of alkalinity is neces sary for their best growth (this being the reason of their development in the in testine), while nearly neutral inedia are very unsuitable, and acids are decidedly inimical to them; hence they cannot live in the stomach. Sulphuric, hydro chloric, and phosphoric acids, fresh lemon-juice and wine and beers contain ing a somewhat large proportion of acids, are all able, in a different degree, to kill them. Among the chemical substances having a marked microbicidal action upon cholera vibrios, the most energetic are corrosive sublimate (1 to 10,000), sulphate of copper (1 to 25,000), and quinine (1 to 5000). Mustard-oil and volatile essences generally display a sim ilar action.
Experitnents showing that a distinct degree of alkalinization was necessary for the best growth of bacilli, while nearly neutral media were very unsuitable. Sul phuric and phosphoric acids were de cidedly- inimical to the development of the germs. A. Stutzer and R. Burri (Zeit.
f. Hygiene u. Infectionskr., B. 14, '93).
Asiatic cholera is a nitrate poisoning, the result of the growth of the specific bacterium. Emmerich and Tsuboi (Miin chener med. Woch., June 20, '93); Klem perer (Berliner klin. Woch., p. 74, '93).
If the theory of Emmerich and Tsuboi upon cholera as the result of nitrate poisoning produced by the bacilli is true, more than one cause must act to produce cholera. Not only are the bacilli neces sary, but the nitrites also, upon which they are to act to produce nitrates. The presence of carbohydrates is a further essential. R. J. Beck (Med. Corres. des wfirttembergischen Arzt. Landesvereins, Dec. 18, 28, '93).
The specific nature of the comma bacilli is proved by their being found clusively in the intestinal contents of choleraic patients; but it is proved, too, by experimental production of a like disease in animals through ingestion or inoculation of their cultures. Indeed, Koch, having previously alkalinized the stomach-contents of guinea-pigs, duced 10 cubic centimetres of broth culture of comma bacilli and ately afterward injected into the peri toneum 1 cubic centimetre of tincture of opium, and succeeded in producing an intestinal lesion with a flaky. rhceal fluid: a pure culture of comma bacilli. Other experimenters,by ing such a culture into the peritoneum.
observed in guinea-pigs and rabbits a very grave disease, with extreme weak ness, low temperature, and death. in col lapse. Inoculations of choleraic virus in man, however, gave no result.
Cholera vibrios vary to a considerable extent in their pathogenic attributes and chromogenic properties, not only when they grow saprophytically outside the body, but also when they are ob tained directly from the intestine of a choleraic patient; so that many forms of them have been described as different organisms, while they are only peculiar varieties of the same germ. Moreover, it seems highly probable that their sym biosis with certain species of microbes found in the dejections and in the in testines of cholera patients play an im portant part in the increase of their virulence, while some other intestinal microbes may, on the contrary, retard their growth an.d lessen their virulence.