466 SPIRILLUM CHOLERJE ASIATICS. 



after the first appearance of the epidemic the treatment 

 of the individual cases is better carried out, that those 

 Avho are in contact with the sick take greater care as 

 regards cleanliness and other precautions, that the 

 majority of the inhabitants take less raw food, that 

 greater care is employed in providing pure water, that 

 the individual predisposition is diminished as far as 

 possible, partly by the avoidance of excesses, partly by 

 early treatment of gastric disturbances, and partly, in 

 the case of another portion of the population, by recovery 

 from a previous mild or severe attack ; and finally, that 

 at times, with the change of the season of the year, one 

 or other of the external influences are removed, and thus 

 the sources of infection, and the ease with which the 

 germs are transported, are diminished. The more com- 

 pletely and quickly all those factors which tend to the 

 extinction of the epidemic come into play the earlier 

 will further infection cease; the longer the one or the 

 other favouring condition continues the further will the 

 epidemic spread. It is evident that in order that cholera 

 should become permanent or endemic in the neighbour- 

 hood other very favourable conditions must be present, 

 especially as regards the climate, and probably still 

 more as regards the habits of life of the population. 



It would lead us too far to explain the various striking 

 phenomena which occur in the epidemic spread of cholera 

 by the factors which come into play, and which have 

 already been mentioned in detail. This much is evident, 

 that the sum of the external factors furnishes a sufficient 

 explanation of numerous epidemiological laws, and also 

 of numerous exceptions; whether it be that in the one 

 case several of these factors act together, and thus 

 increase the effect, or whether it be that one or other are 

 in opposition to, and thus neutralise each other, there 

 are a number of possible explanations which may corre- 

 spond to as many variations in the occurrence of cholera. 

 For many persons the extraordinary multiplicity of the 

 factors which furnish the explanation of the local and 

 seasonal distribution of cholera is self-evident; this is 

 more especially the case since Virchow drew attention so 



