62 6 THE POPULAR SCIENCE MONTHLY. 



in harmony with the conditions of soil and subsoil water. This is un- 

 fortunately still the darkest chapter in the book, and will probably 

 remain so ; but it is not darker than the explanation of the nature of 

 another infectious disease, which is equally dependent on conditions 

 of soil and water — namely, malarial fever. We are firmly convinced 

 of its telluric and climatic origin, and yet a study of Von Hirsch's 

 "Handbook on Historio-Geographical Pathology " shows how little we 

 know. Whether the infective material gets to man from the air, or 

 water^ or food, or the sting of a gnat, and so forth, we know not ; and 

 if we examine the tables showing the appearance of ague in the differ- 

 ent months of the year in Leipsic, Vienna, etc., we come to see that 

 the tables are not so very different from those drawn up by Brauser 

 on cholera. In malarial fevers it is doubted whether infection is con- 

 veyed by the drinking-water, whereas contagionists believe that chol- 

 era is propagated through this source. The drinking-water theory 

 played a great part in the causation of epidemics in the middle ages ; 

 it was believed that wicked men, either Jews or Christians, had poi- 

 soned the springs from which death was drunk. For good health, pure 

 water is as necessaiy as pure air, good food, comfortable quarters, and 

 so forth. I myself am an enthusiast in the matter of drinking-water, 

 but not from fear of cholera or typhoid fever, but simply from a pure 

 love for the good. For the water is not only a necessary article of 

 food, but a real pleasure, which I prefer, and believe to be more 

 healthful than good wine or good beer. When water fails, man may 

 suffer not only from cholera, but from all possible diseases. In places 

 where cholera prevails the water may always be indicted, for the 

 water-supply is always a part of the locality, and the doctrine will fre- 

 quently hold good, because the part may be mistaken for the whole. 

 Where the influence of the water is held up to the exclusion of all 

 other local factors error is liable to creep in. In England, where the 

 drinking-water theory is fully believed in, two like influences, in which 

 every other local factor was excluded, were observed in the cholera 

 epidemic of 1854. In one case, in a street in London which was sup- 

 plied by two water companies, the Lambeth with pure water, and the 

 Vauxhall with impure water, it was found that the cholera was practi- 

 cally limited to the houses supplied by the Vauxhall Company. I was 

 so much impressed by this fact that I endeavored to see whether the 

 epidemic of 1854 in Munich could not be explained on a similar hy- 

 pothesis. But my researches led me to a negative result. Without 

 doubting the facts observed in London, I am of opinion that the im- 

 pure water of the Vauxhall Company did not spread the germs of 

 cholera, for the propagation of cholera was not effected by this means 

 in Munich, but that the water increased either the personal predisposi- 

 tion to cholera, or perhaps the local predisposition, since the water 

 would be employed in the houses, and about the soil. Later on, in 

 1866, Letheby doubted the accuracy of the drinking-water theory, and 



