312 PATHOGENIC BACTERIA. 



year when there are not at least some cases of cholera 

 in the city. 



The frequent pilgrimages and great festivals of the 

 Hindoos and Moslems, by bringing together an enormous 

 number of people who crowd in close quarters where filth 

 and bad diet are common, cause a rapid increase in the 

 number of cases during these periods and the dispersion 

 of the disease when the festivals break up. The disease 

 extends readily along the regular lines of travel, visiting 

 town after town, until from Asia it has frequently ex- 

 tended into Europe, and by the steamships plying on 

 foreign waters has been several times carried to our own 

 continent and to the islands of the seas. Many cases are 

 on record which show conclusively how a single ship, 

 having a few cholera cases on board, may be the cause 

 of an outbreak of the disease in the port at which it 

 arrives. 



It seems strange to us now, with the light of present 

 information illuminating the pages of the past, to observe 

 how the distinctly infectious nature of such a disease 

 could be overlooked in the search for some atmospheric 

 or climatic cause, some miasm, which was to account 

 for it. 



The discovery of the organism which seems to be the 

 specific cause of cholera was made by Koch, who was 

 appointed one of a German cholera-commission to study 

 the disease in Egypt and India in 1883-84. Since his 

 discovery, but a decade ago, the works upon cholera and 

 the published investigations to which the spirillum has 

 been subjected have produced an immense literature, 

 a large part of which was stimulated by the Hamburg 

 epidemic of a few years ago. 



The micro-organism described by Koch, and now gen- 

 erally accepted to be the cause of cholera, is a short 

 individual about half the length of a tubercle bacillus, 

 considerably stouter, and distinctly curved, so that the 

 original name by which it was known was the "comma 

 bacillus" (Figs. 80, 81). 



