“The contemporaneous appearance of variola and rubeola represents the first manifestation of an epidemic constitution, resulting from a collection of unknown influences as to their nature, but manifest by their effects. The earth was from thence prepared to receive scarlatina, and it soon came to bear its baleful fruits. We do meet some mention of scarlet fever in the writings of the Arabian School, but it is merely suspected and only vaguely indicated. But when we remember how difficult it often is to diagnose at first between variola and measles, we are not astonished at the indecision manifested in adding another exanthematous affection to the medical incognito. It was only after innumerable observations and the experience of several centuries that the third new disease received its nosological baptism. There is nothing to prove that it did not co-operate with earlier epidemics of variola and rubeola, remaining undistinguished as to type, however.” What clearly proves that there was confusion between the various fevers of exanthemata is that Ingrassias describes scarlatina in 1510, under the name of _rosallia_, adding, “Some think the measles and _rosallia_ are the same malady; as for me, I have determined their differences on many occasions. _Nonnulli sunt qui morbillos idem cum rossalia esse existimant. Nos autem soepissime distinctos esse affectus, nostrismet oculis, non aliorum duntaxat relationi confidentes inspeximus._”[24] These facts appear conclusive enough to admit that measles and scarlet fever are, like variola, the products of the epidemic constitution developed during the sixth century, as contemporaries of the bubonic plague, all these maladies representing the medical constitution of the first centuries of the Middle Age. THE SWEATING SICKNESS OF ENGLAND. The name of Sweating Sickness was given to the great epidemic of fever that appeared in England in the fifteenth century, and from thence extended over Continental Europe. This epidemic broke out in the month of September, 1486, in the army of Henry VII., encamped in Wales, and soon reached London, extending over the British Isles with frightful rapidity. Its appearance was alarming and during its duration, which was only a month, it made a considerable number of victims. “It was so terrible and so acute that within the memory of man none had seen its like.”