THE RELATIONS OF THE SOIL TO HEALTH. 185 



become very active in the moist stratum, and large quantities of carbonic acid 

 and other inorganic compounds are produced. If the germs of infectious or con- 

 tagious diseases have been introduced into the soil, they also multiply, and may 

 escape with the movements of the ground air into the external atmosphere, and 

 there produce their infective action. 



This, it is held by Pettenkofer and his followers, is what actually occurs in 

 cholera and typhoid fever. Prof. De Chaumont has laid down the lule that a 

 soil with a persistently low stage of ground water, say fifteen feet below the sur- 

 face of the ground, is healthy ; a persistently high stage of ground water, less 

 than five feet below the surface, is unhealthy, while a fluctuating level of the 

 ground water, especially if the changes are sudden and violent, is very unhealthy. 

 This would lead us to expect that places where this fluctuation is very great would 

 show a large mortality from such diseases as are attributed to impurities in the 

 soil. And this we find especially true in India. In certain localities in India, 

 cholera, for example, is endemic — that is to say, the disease is never entirely 

 absent in such localities. Calcutta is one of these places. The rainy season 

 begins about the first of May and continues until the end of October. During 

 the next six months there is very little rain. It is fair to assume that the ground 

 water rises during the rainy season, and checks decay and the multiplication of 

 the germs of the disease in the soil, and that these processes become more active 

 as the dry season advances and the ground water level fafls. If we note the 

 death-rate from cholera in Calcutta, it will be found that it bears a distinct rela- 

 tion to the movement of the ground water. The deaths from cholera begin to 

 increase from. October, and reach their height in April. Dr. Macpherson, who 

 has written a very elaborate history of Asiatic cholera, shows this relation very 

 clearly. For twenty-six years the average annual rainfall was sixty-three inches. 

 From May to October fifty-seven inches fell, while the remaining six inches fell 

 from November to April. The average number of deaths from cholera annually 

 was 4,013. Of these, 1,238 died in the rainy season, while 2,775 — nearly three- 

 fourths — died during the period of dry weather. 



In the cholera epidemics of 1866 and 1873 '^^ Buda-Pesth, the same relations 

 existed between the ground water and the cholera. As the level of the ground 

 water rose, the cholera diminished, while the disease increased upon the sinking of 

 the ground water. Exactly the same behavior was exhibited by the disease in 

 Munich in 1873. 



There seems good reason to believe that typhoid fever is propagated in con- 

 sequence of movements of the ground water, in the same way as above explained 

 for cholera. This does not exclude the infection of drinking water by the disease 

 germ, since much of the drinking water used, as before stated, fs drawn from. the 

 ground water. Pettenkofer, Buhl, and Virchow have shown that the death-rate 

 from typhoid fever has a distinct and definite relation to the ground water oscilla- 

 tions. This has been incontestably proved for two cities, Munich and Berlin. 

 When the level of the ground water is above the average, typhoid fever decreases; 

 when it is below the average, the number of cases becomes greater. 



