in harmony with the conditions of soil and subsoil water. This is unfortunately 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 different 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 conveyed by the drinking-water, whereas contagionists believe that cholera 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 poisoned the springs from which death was drunk. For good health, pure water is as necessary 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 frequently 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 supplied by two water companies, the Lambeth with pure water, and the Vauxhall with impure water, it was found that the cholera was practically 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 hypothesis. But my researches led me to a negative result. Without doubting the facts observed in London, I am of opinion that the impure 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 predisposition 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
