hung like an incubus upon all endeavors to ascertain the nature of the vital processes, and gave a bias to every effort to determine the secret of their production. For centuries the agency of the rational soul was the phantom of medical philosophers, who deviated from the natural history arrangement of the vital actions devised by Aristotle, and, not content to study them in their manifestations to the senses, plunged headlong into the pit of blind, conjectural subtleties connected with causation. The idea that a vital principle existed, and modified the structural operations of the body, was obscurely seen by Van Helmont and Paracelsus, and to their imagination became a presiding deity, or demon. The rational soul, the anima of Stahl, was but another form of the same fancy, which figured, even in the middle of the eighteenth century, in the explanation of the vital processes by so accurate and meritorious an observer as Prof. Whytt.[1] That Stahl himself had little faith in his own enunciation, and that he made it in deference to the authority of the schoolmen, he admits, when he informs us that the “introduction of the rational soul into his medical theory was not at all necessary to its vitality, and assigns as a reason for having recourse to that principle, his fear of being suspected to maintain that certain corporeal actions could be performed without an agent.”[2] To this ancient delusion Des Cartes administered the coup de grace by denying the existence and co-operation of a sentient soul in the production of the animal functions, and showing that the vital processes may be executed independently of mental co-operation. The teachings of Hoffman and Boerhaave were in accordance with the Cartesian philosophy; when the last shadow of pagan theism and clerical superstition vanished from sight forever.
We have alluded to the foreign origin of the physicians who first settled in the colonies, and to the education of those who, at an early period, went abroad to the University of Leyden, where Boerhaave was the presiding genius. He was the dictator of medical opinions, not only on the Continent,
