Page:Popular Science Monthly Volume 62.djvu/362

356 of 15,934 out of a total number of cases exceeding 74,000. In this epidemic the disease followed the Mississippi River 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 southern 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 measures which have been proved to be effective in preventing its propagation. 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 conditions 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 habitations. 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 attending 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