applied. Whence comes it that from any given exposure to an exciting cause, no two persons will be affected alike, or in the same degree? Some may suffer severely, others be slightly affected, while by far the greater number will escape altogether. This simple fact of familiar occurrence might have sufficed to direct a greater share of attention to the predisposition, on which exciting causes operate. Of the prevailing error, the mischief is two-fold, for, in attributing an undue importance to an exciting cause, it assumes a principle which can be of very little avail in directing the treatment, while, on recovery, it begets further error, by inducing a greater solicitude to avoid the exciting cause, than to keep the constitution in that healthful state which would prove the best preservative.
Ordinary maladies, however suddenly the parties may appear to be seized, are never of sudden occurrence. The special suffering which first arrests attention may suddenly arise, but this is always preceded, and for a considerable time, by sensible deviations from that equable and temperate performance of function which can alone constitute sound health. The common exciting causes to which so many of our ordinary maladies are imputed, and from which they doubtless in part arise, never produce their effects save on constitutions prepared to suffer by their influence. The instances of disease from morbid poisons, such as contagions, miasmata, and such like, may appear exceptions; but they are really not so. All who are so exposed do not suffer, and in those who become affected, the degree of suffering is dependant less on the intensity of the
