PREVENTIVE MEDICINE. 357 



fever, provided, of course, that the sewers are used for the purpose for 

 which they are inteuded, aud that streets and back yards no longer serve 

 as receptacles for filth, as was usual during the presanitary period even 

 in great cities like London and Paris. The axiom 'tout a l'egout' now 

 governs the practice not only in Paris, but wherever the fundamental 

 principles of municipal sanitation are understood and sewers have been 

 constructed. Unfortunately, the cost of sewer construction, the re- 

 luctance of tax-payers to part with their money and the ignorance 

 or indifference of municipal authorities have conspired to prevent the 

 accomplishment of this fundamental sanitary measure in very many 

 towns in the United States, and our endemic plague typhoid fever 

 continues to claim a large annual quota of victims in such localities. 

 Even in the national capital our sewer system is incomplete and in 

 many out-of-the-way places, especially in the densely populated alleys 

 of the city, shallow box privies are in use as receptacles for human 

 excreta and the typhoid fever rate, owing to this and other causes, is 

 disgracefully high. 



Mortality rates in towns and cities throughout the civilized world 

 depend to a large extent upon the purity of the water-supply and the 

 efficiency of the system of sewage disposal; and the constant improve- 

 ment which is shown by the mortality statistics of England and other 

 countries which have made the most progress in this direction is un- 

 doubtedly largely due to these two factors. This is well illustrated by 

 the mortality statistics of armies. In the German army the annual 

 death-rate in 1868 was 6.9 per thousand, a decade later it was 4.82, in 

 1888 it had fallen to 3.24 and in 1896 to 2.6. In our own army, the 

 death-rate during the period of peace just prior to the Mexican War 

 (1848) was about three and one half times as great as during the five 

 years preceding our recent war with Spain, and since the year 1872 

 there has been a diminution of the death-rate of nearly forty per cent. 

 In the British army at home stations the mortality rate during the 

 decade ending in 1884 was 7.2 per thousand, in 1889 the rate had 

 fallen to 4.57 and in 1897 to 3.42. In the Italian army there has been 

 a gradual and progressive reduction from 13.3 per thousand in 1875 

 to 4.2 in 1897. The mortality in the French army was a little over 

 21 per thousand during the five years ending in 1825. In 1890 it had 

 fallen to 5.81 per thousand. 



According to the best estimates the average of human life in the 

 sixteenth century was somewhat less than twenty years. At the present 

 time it is more than twice as long and during the past twenty-five years 

 the average duration of life has been lengthened about six years. During 

 the first thirty-five years of the past century the vital statistics of the 

 city of London showed a mortality of about 29 per thousand. At the 

 present time the mortality in that great city has been reduced to from 



