374 TEXT-BOOK OF BACTEKIOLOGT. 



peculiarities of their progress gathered by close observations of 

 cholera epidemics cannot always be accounted for by the view just 

 discussed. But many of these observations have been made at a 

 time where points now regarded as most essential were not at all 

 known and, hence, could not be considered. It is, indeed, certain 

 that there are places strikingly free from contagion in a completely 

 pestilential neighborhood, and the cause of this immunity has not 

 in every case been explained. Numerous epidemiological prob- 

 lems are waiting solution; even local and temporal disposition may, 

 in a correspondingly altered condition, be of importance in the 

 origin of cholera. 



But although the comma bacillus and our knowledge of its 

 nature do not yet account for everything, we may recall the sen- 

 tences with which Virchow established (in the second cholera con- 

 ference) his standpoint. In remarking that a particular disease of 

 the silk-worms (muscardine) was the oldest of the mykotic affec- 

 tions thoroughly investigated and that the parasitic cause of an 

 epidemic disease had first been established in said muscardine, he 

 pointed to the fact that this disease had been known so long and 

 studied so zealously and that so many means had already been 

 used to fight it, and added: "And yet we cannot even to-day state 

 \Aith entire certainty what are the reasons for its appearing alter- 

 nately in greater or less extent, nor can one say what one must do 

 to suppress it." And he declares afterward : " During my studies 

 of natural sciences I have always been inclined, whenever an obser- 

 vation has been made in a single concrete case under every guar- 

 antee of certainty, not to make the acknowledgment of the correct- 

 ness of such an observation dependent on its ability of accounting 

 for everytliing." 



" Cholera is a disease endemic in certain districts of India, espe- 

 cially in Lower Bengal, the Ganges Delta proper, and from time 

 to time has been brought to our country. Its cause is a specific 

 bacterium. This passes from man to man by means of moist 

 agencies, especially the drinking-water; is received with the food, 

 and being developed in the intestine gives rise to cholera. Its 

 entrance and increase are probably facilitated by a certain favora- 

 ble condition of the intestinal canal, an individual predisposition, to 

 be accounted for, perhaps, by a diminution of the acidity of the 

 stomach and inertia of peristalsis." 



The symptoms of cholera admit of no doubt that the intestine is 

 the real seat of the pathological processes; for the symptoms 

 referable to the digestive canal predominate. Frequent watery, 

 nearly colorless and odorless discharges of the appearance of whey 



