In all such cases the sickness which ensued among the healthy from contact with strangers had a more or less definite type; and that type in each case must have been determined mainly by the antecedents of the strangers, their racial characters being reckoned among the antecedents as well as their special hardships and their personal habits. In the case of the singular visitation of England in 1485, the strangers were a swarm of disreputable free-booters from Normandy, natives of a soil which developed the sweat as an indigenous malady in the long course of generations. If they themselves had shown the symptoms of the sweat in 1485, one might have said that the circumstances of their passage in crowded ships, of their exhausting march from Wales to Leicestershire, and thence to London, had brought to the definite issue of a specific disease that which was otherwise no more than a habit of body, a constitutional tendency, a disease in the making. But there is no reason to suppose that they themselves incurred the symptoms of the disease at all; it was contact with them in England, particularly in London, that determined the peculiar type of disease in others. Those others were of a different national stock, and for the most part of another manner of life; in their very differences lay their liability, according to well-known analogies. Of course there must have been something material, something more than abstract contact, to cause the sweat in certain Englishmen; and although we cannot image the form of the virulent matter, we are safe to pronounce, in this hypothesis, that it must have come from the persons of the foreign soldiery. The Habitat of the Virus. We may go even farther in the way of specific probability, and bring the virus definitely to a habitat in the soil. The English sweat, like the Picardy sweat itself, had certain characters of a soil poison, like the poison of cholera, yellow fever and typhoid fever; only it was not endemic like the two last, but periodic, as well as somewhat volatile in its manner of travelling, like dengue, influenza, and others of the “posting” fevers of former times. This brings us to the singular history of the epidemics of sweat in England,--to the clear intervals of many years and the sudden bursting forth anew. What became of the specific virus from 1485 to 1508, to 1517 to 1528, to 1551, and after?