When the cholera first appeared in Europe and in this country in its epidemic form, the majority of medical men, as well as the people, believed it to be contagious, and to be propagated solely on this principle. But when the disease appeared in 1848 a decided change of opinion occurred, which led to a full discussion of the subject, without any definite result; and the great question as to its contagious character and its mode of propagation remains still unsettled. The higher authorities, says an eminent author, concurred in the opinion of the Board of Health, "that the disease was not in any way contagious, and that no danger was incurred by attendance on the sick." A large body of evidence, however, has been exhibited, going to show that human intercourse has, at least, a share in the propagation of the disease, and that it, under some circumstances, is the most important, if not the sole means of effecting its diffusion. On the other hand, it is affirmed that though it may be communicated, in some cases, by the agency of human intercourse, it does not follow that the material cause spreads by true contagion, that is, by reproducing itself in the bodies of men, and there only. The disease may be carried by healthy persons in their clothing, in their ships, and in their caravans. That instances of this kind have occurred there can be no question, for numerous records present some undoubted instances of the occasional communication of the cholera-poison through human intercourse; still it is no less certain that its general extension over the world cannot be accounted for on this principle alone. "Its propagation by this means seems to be the rare exception, its spread over the earth from other causes being the common rule." Dr. Hamlin, writing from Constantinople, in reference to the recent irruption and prevalence of the cholera in that city, observes, "The idea of contagion should be abandoned. All the missionaries who have been most with the most malignant cases, day after day, are fully convinced of the non-contagiousness of the cholera. The incipient attacks which all have suffered from are to be attributed to great fatigue, making the constitution liable to an attack."