356 POPULAR SCIENCE MONTHLY. 



of 15,934 out of a total number of cases exceeding 74,000. In this 

 epidemic the disease followed the Mississippi Eiver to the very suburbs 

 of St. Louis, and the state of Tennessee suffered severely as well as the 

 states south of it. The city of Memphis alone had a mortality from the 

 disease of about 5,000. These repeated epidemics not only cost the 

 lives of thousands of citizens and paralyzed business of all kinds during 

 their prevalence, but apprehension with reference to the recurrence of 

 the disease very materially interfered with the growth of many south- 

 ern cities and retarded greatly the development of those portions of the 

 country most liable to invasion. All this is now changed ; public health 

 officials are no longer filled with apprehension upon the approach of 

 summer by the thought that any ship arriving from Havana may 

 introduce the deadly pestilence to our shores; commerce is no longer 

 subjected to the serious restrictions formerly considered necessary for 

 the exclusion of the disease ; and the public generally have been made 

 aware that the fangs of this threatening monster have been drawn by 

 the scientific demonstration of its mode of attack and the simple meas- 

 ures which have been proved to be effective in preventing its propaga- 

 tion. Until the recent demonstration of the transmission of yellow 

 fever by mosquitoes, this disease was generally regarded as one of the 

 filth diseases, although there were many facts opposed to this view. 

 In the light of our present knowledge we can no longer class it with 

 typhoid fever, cholera, bubonic plague and dysentery, in which diseases 

 the germ is known to be present in the alvine discharges of the sick and 

 which are, consequently, well named filth diseases. 



We now see clearly, however, why in certain particulars relating to 

 its etiology it resembles the malarial fevers. It is limited as regards 

 its prevalence to comparatively warm latitudes or to the summer 

 months in more temperate regions and is dependent, to a certain extent, 

 upon rainfall or the proximity of standing water, because these condi- 

 tions are necessary for the propagation of mosquitoes. As regards the 

 filth diseases, properly so-called, no single agency is more important for 

 their prevention than the use of properly constructed sewers for the 

 reception of excreta and its removal from the vicinity of human habita- 

 tions. Sewers had come into use and had the warm endorsement of 

 sanitarians long before the discovery of the germs of the infectious 

 maladies under discussion, and before it was positively known that 

 the infectious agent in these diseases is contained in the discharges 

 from the bowels. But now that we have an exact knowledge of the 

 etiology of these diseases, the reason for the beneficent results attend- 

 ing the use of sewers, in connection with an ample and pure water 

 supply, is apparent. It may be safely asserted that a city or town 

 having a complete and satisfactory sewer system and a pure water 

 supply is practically immune from epidemics of cholera or typhoid 



