external objects, when acted upon, convey the subject of thought to the
nervous fibres of the brain; and while the mind is employed in thinking,
the part of the brain is in a greater or less degree of motion; a large
quantity of blood is transmitted to the brain, the action of the
arteries become increased, and the nervous system sensibly affected.

Plato has remarked, with reference to the influence of the mind on the
corporeal frame, "Where the action of the soul is too powerful, it
attacks the body so powerfully that it throws it into a consuming state;
if the soul exerts itself in a peculiar manner on certain occasions, the
body is made sensible of it, for it becomes heated and debilitated." An
Italian physician also observes on this subject, that the union of the
soul with the body is so intimate, that they reciprocally share the good
or evil which happens to either of them. The mind cannot put forth its
powers when the body is tired with inordinate exercise and too close
application to study destroys the body by dissipating the animal spirits
which are necessary to recruit it.[2]

The knowledge of the influence of the passions of the mind over the
bodily functions, is of ancient date. Plato, in his "_Timaeus_,"
states it as his firm conviction, that the spirit exerted a marked
influence in producing disease. This opinion was afterwards revived by
Helmont, Hesper Doloeus, and Stahl; the latter plainly says, that the
rational soul presides over and directs the animal functions. In this
doctrine he was followed by Nichols, in his "_Anima Medica_."
According to the doctrines of Stahl, the disorders of the body proceed
principally from the mind; and, according as it is variously affected,
it produces different effects (diseases.) Hence, when the mind, which
animates the most robust and best organized body, is violently agitated
by fright, rage, grief, vehement desire, or any other passion, whether