There has been and continues to be a popular impression of the importation or the contagiousness of disease, created by the frequent occurrence of epidemic diseases amongst itinerant classes of the population. Seeing the occurrence of such diseases amongst those who travel, it is an easy and apparently a natural inference that the diseases are carried by them. Thus, the low tramps’ lodging-houses in our towns were in the Sanitary Report shown to be throughout the country the worst of fever-nests in each place; but they were also shown at the same time to be the places where there was the most overcrowding and the greatest filth. With a stationary population, with the same overcrowding and filth, it may be confidently pronounced that the disease would be worse. When by bad weather the tramps are detained and kept stationary, it is worse. The tramping about from town to town and in the open air—the movement which to superficial observation imports the disease—in reality mitigates it. From what we have already said, it is consistent with this general statement that tramps infected with fever in one place may carry it with them and spread infection in another place amongst classes of persons predisposed by the like habits and conditions, as was exemplified in the spreading of the Pali plague. Of late times the poor Irish emigrants are said to have imported fever into this country; they are represented, for example, to have imported fever into Liverpool; but the description of the places where the fever burst out, and the overcrowding in them, displayed fever-nests sufficient to have produced fatal results on the most robust of the stationary populations. “In one small cellar with no window,” a gentleman, who ministered to the wants of the poor people who had crept for shelter into damp uninhabited houses, and who, it was stated, fell a victim to the contagious nature of the fever, found “eighteen persons in fever, lying on wet dirty straw. In one house he counted eighty-one, in another sixty-one, in every stage of fever, on straw in the corners.” It would be surprising if the poor Irish had not imported fever into the lower districts of towns, when, as in Glasgow, they have added 10,000 annually to the already overcrowded and wretched population of that city; just as the miserable refugees from the infected villages of Ragpootana carried the pestilence into the close, filthy, and already overcrowded huts of the neighbouring villages. But the conditions in which the Irish emigrants have arrived, and have been crowded together in the towns as well as on shipboard, are just the conditions in which fevers arise amidst stationary populations; and, we may confidently state, would have been worse had the particular class of migrants been stationary.