its gates closed for an unusually long time, and the disease were in its neighborhood.
The reports of the cholera commission for the German Empire contain a large number of proofs of the influence of the locality, particularly of the soil, among which I might especially mention the reports of Gunther on the spread of cholera in the kingdom of Saxony, and of Pistor on the government district of Oppeln. Both these investigators, not satisfied with considering only the last visitation of cholera in 1872-'74, have also included within the circle of their inquiry all the outbreaks that have come to knowledge since the appearance of the disease in Europe in 1832. The confirmation of the localistic theory of cholera and other epidemics can no longer be put in question; and, if it were the only result reached by the German cholera commission, the money appropriated to the investigation would have been well spent.
We may now ask, What can there be in the soil that can exert so powerful an operation for good or evil upon our health? To this question, so far as concerns injury to health, the answer may be returned that, in all probability, the property is derived from the minute organisms or their products, of which many million individuals can be put within the area of the head of a pin, and which inhabit the porous soil from the surface down to a great depth—organisms which are capable of being injurious or harmless, or even useful to us, as we are already acquainted with injurious and harmless and useful plants and animals. They have heretofore been invisible to us, having only just been brought to knowledge, in the course of recent investigations in vegetable and animal physiology and pathology, by means of the microscope and experimental cultivation. A prominent vegetable physiologist, Naegelli, has accurately and clearly described them with direct reference to their hygienic significance in his well-known work, "Die niederen Pilze in ihren Beziehungen zu den Infectionskrankheiten und der Gesundheitspflege." Their mysterious presence recalls the ancient belief in invisible spirits that were accustomed to rise out of the earth, float in the water, and cast gloom over the spots haunted by them. Naegelli called a soil that produces or favors epidemics a disease-bearing (Siechhaft), and its opposite a healthful (Siechfrei) soil. We must not conclude that only a locality of the former kind harbors molds and similar lower organisms, and one of the latter kino does not, or that these organisms reach us only from the former and not from the latter; on the contrary, they are always present everywhere. If they sometimes appear deleterious, at other times harmless, the conviction is forced upon us, either that the same species do not occur universally, or that the same species assume different properties at different places, under different circumstances, and at different limes; that is, that they are only here and there and occasionally poisonous. If either is the case, the medium in which tiny
