3 oo POPULAR SCIENCE MONTHLY. 



nated by such germs, and it has been shown with a great degree 

 of probability that such contamination frequently results from the 

 transportation of infectious material from the surface of the 

 ground, from shallow pits, etc., by flies, which after visiting the 

 most filthy places, may alight upon a beefsteak or fall into the milk 

 jug in a well-ordered kitchen. But by far the larger number of 

 cases result from drinking water containing the cholera germ. 



The epidemic extension of cholera depends upon climatic condi- 

 tions to a much greater extent than does that of typhoid fever. It 

 is especially a disease of hot climates, and of the summer months in 

 temperate regions. The disease may be propagated during the win- 

 ter, even in cold climates, by the occurrence of a series of cases in 

 localities especially favorable for such propagation, and in this case a 

 recrudescence of the epidemic usually occurs during the following 

 summer. In Russia, during the years 1853 to 1855, nearly two hun- 

 dred and fifty thousand deaths occurred during the months of June, 

 July, August, and September, and less than twenty-five thousand 

 during the remaining months of the year. In 1832 cholera was in- 

 troduced into Canada by emigrants from Ireland, and spread rapidly 

 in the valley of the St. Lawrence. An independent importation dur- 

 ing the same year brought it to New York and to New Orleans, from 

 which points it obtained a tolerably wide diffusion in the United 

 States. In 1835 it appeared for the first time in South America, on 

 the coast of Guiana. North America was again visited by the scourge 

 in 1848, and it continued to prevail in the United States and Mexico 

 for several years, especially in 1849 to 1850. In the West Indies it 

 caused a considerable mortality in the period from 1850 to 1854. 

 During the year 1854 it again became widely prevalent in the 

 United States. In 1865 the West Indies suffered from another 

 severe epidemic, and in the following year the disease again estab- 

 lished itself at three widely separated seaports in North America — 

 Halifax, New York, and New Orleans. From the last-mentioned 

 port it extended throughout the Mississippi Valley. During the 

 years 1865 to 1868 the disease also committed great ravages in some 

 of the South American countries not previously visited by it, and 

 especially in Brazil, Paraguay, Uruguay, and the Argentine Repub- 

 lic. In 1873 cholera was again imported to New Orleans and spread 

 throughout a considerable portion of the Mississippi Valley. Our 

 exemption from an epidemic during the recent widespread prevalence 

 of the disease in Europe is, no doubt, due to the efficient methods for 

 its exclusion adopted at our ports of entry, and especially at NTew 

 York, where several cholera-infected ships arrived during the height 

 of the Hamburg epidemic of 1892. 



Yellow fever is essentially a disease of the littoral, and especially 



