deep parts of the body; that when Nature requires the help of a fever, whereby she may be able to separate the vitiated particles from the blood, or otherwise expel them, either by a sweat, a looseness, or some kind of eruption, she accomplishes this object in the whole mass of blood, and that by a violent motion of the parts; that when this object is accomplished suddenly, either by the health or death of the patient, the disease is acute; when, on the contrary, the matter of the disease is of such a nature that it cannot have the assistance of a fever for the separation of it; or when this kind of matter is fixed to any particular part, which is unable to exclude it, or when the blood is vitiated by the continual flow of new matter into it, in these cases, the matter being very slowly or not at all concocted, the diseases which proceed from such unconcocted matter are called chronic: that acute diseases proceed from a secret and inexplicable alteration of the air infecting men’s bodies; that these diseases do not at all depend on a peculiar crasis of the blood and humours any otherwise than the occult influence of the air has imprinted the same upon them; that they continue as long as this secret constitution of the air and no longer; that they do not come at any other time; and that these constitute epidemic fevers; that, on the other hand, acute diseases arise from this or that particular irregularity of particular bodies, which, because they are not produced by a general cause, do not therefore invade many at once; that this species comes every year, and at any time of the year; and that these may be called intercurrent or sporadic, because they happen at any time during the prevalence of epidemics.[2]”