exhausts the spirits, destroys the strength, enervates the mind, makes
us pusillanimous, unable either to bear fatigue, or to keep our passions
under."[3]

Shakspeare appears to have formed a just conception of the great injury
which the corporeal frame experiences from a too close application of
mind. The immortal bard observes,--

"----Universal plodding poisons up
The nimble spirits in the arteries
As motion and long-during action tires
The sinewy vigour of the traveller."

_Love's Labour Lost._

In the consultations of Wesper we find related the history of a young
man of family 22 years of age, who, having applied himself incessantly
to intense mental exertion, was seized with a fit of insanity, in which
fit he wounded several persons and killed his keeper. Catalepsy has been
known to have been produced by great mental application. Fomelius gives
us a remarkable instance of it. A man (says he) who passed whole nights
in writing and studying, was suddenly attacked with a fit of catalepsy:
all his limbs stiffened in the attitude he was in when the disease first
seized him. He remained upon his seat, holding the pen in his hand, and
with his eyes fixed on his paper, so that he was considered to be still
at his studies, till being called to, and then shaken, he was found to
be without motion or sensation.[4]

Many extraordinary instances are on record, of remarkable changes having
been produced in birds by an affection of the animal passions. The