observed in Munich in 1873 and 1874, can be explained only by reference to the conditions of the soil as to moisture. The epidemic began at the end of an abnormally dry July, prevailed with extraordinary violence till the beginning of August, became stationary about two weeks afterward, and seemed wholly to have disappeared at the end of October, only to break out anew with greater violence in November after a long spell of dry weather, and continued till the end of April, 1874. The city of Augsburg, nine miles from Munich, suffered more severely in proportion than that city in 1874, but was quite free from cholera in 1873, notwithstanding many cases were introduced. It had thirty per cent more rain in that year than Munich.
I can not go further into the consideration of these circumstances; I only cite them as evidence of the influence of moisture in the soil so far as it is measurable by the proportion of ground-water present. We are more nearly concerned with the relation of the soil to the water which we apply to our own use, which we draw from wells and springs, to water as a vehicle conveying matters out from the soil. When typhus or cholera rages epidemically in any place, two parties immediately set up a contention as to whether the epidemic influence proceeds from the water or the air. It must be admitted henceforth that either is possible, that a so-called sickly soil can impart its noxious properties equally to the water and to the air it contains, but it may also be that only one of these ways is possible as to certain matters and lower organisms. Observation and experiment must decide upon that. Most physicians have hitherto considered that infection was probably most directly conveyed through the water, and the so-called drinking-water theory has been developed from this view. It has, however, been ascertained that the best known infectious agent in the soil, the Bacillus malariæ, which Klebs and Tommasi-Crudelli have discovered and studied in the Roman fever-districts, can not live without air. These investigators found that the malarial poison was not communicated to the water that stood over a richly malarious mud. Tommasi says, in his latest work on the Roman malaria and the ancient drainage of the Roman hills, that "the Bacillus malariæ is preeminently an air-living organism." Among the conditions favorable to its propagation in a malarial soil—which need not be a swamp-soil—Tommasi specifies a temperature of about 20° C. (68° Fahr.), a moderate degree of steady moisture, and the direct action of the oxygen of the air on all parts of the mass. He says further, "The lack of one of these conditions is enough to cause a suspension of the development of the spores and of the increase of the malarial ferment." If any one, however, believes that this organism must also remain inoperative when it passes into our blood because that is a fluid, he should be reminded that it makes a great difference whether we put such organism, taken from their airy nests in a moist soil, into cold water, or into warm blood where air is supplied to them from the corpuscles.