The epidemic fever of 1661, according to Willis. On the very threshold of the period at which the history is resumed in this volume, we find a minute account by Willis of an epidemic in the year 1661, which at once raises the question whether a certain species of infectious fever did really exist at that time which exists no longer, or whether Willis described as “a fever of the brain and nervous stock” what we now call enteric fever. Willis’s fever corresponds in every respect to the worm fever, the comatose fever, the remittent fever of children, the acute fever with dumbness, the convulsive fever, which was often recorded by the medical annalists and other systematic observers as late as the beginning of the 19th century[5]. It ceased at length to be recorded or described, and it has been supposed that it was really the infantile or children’s part of enteric fever, which had occurred in former times as now[6]. The epidemic fever which Willis saw in the summer of 1661, after a clear interval of two years from the great epidemics of agues, with influenzas, in 1657-59, is called by him “a certain irregular and unaccustomed fever[7].” It was not, however, new to him altogether; for he had seen the same type, and kept notes of the cases, in a particular household at Oxford in 1655, as well as on other occasions. It was an epidemical fever “chiefly infestous to the brain and nervous stock.” It raged mostly among children and youths, and was wont to affect them with a long and, as it were, a chronical sickness. When it attacked the old or middle-aged, which was more rarely, it did sooner and more certainly kill. It ran through whole families, not only in Oxford and the neighbouring parts, “but in the countries at a great distance, as I heard from physicians dwelling in other places.” Among those other witnesses, we shall call Sydenham; but meanwhile let us hear Willis, whose account is the fullest and least warped by theory.