3. The contractions of the larger muscles of our bodies, that are most
frequently connected with volition, were originally excited into action by
internal irritations: as appears from the stretching or yawning of all
animals after long sleep. In the beginning of some fevers this irritation
of the muscles produces perpetual stretching and yawning; in other periods
of fever an universal restlessness arises from the same cause, the patient
changing the attitude of his body every minute. The repeated struggles of
the foetus in the uterus must be owing to this internal irritation: for the
foetus can have no other inducement to move its limbs but the tædium or
irksomeness of a continued posture.

The following case evinces, that the motions of stretching the limbs after
a continued attitude are not always owing to the power of the will. Mr.
Dean, a mason, of Austry in Leicestershire, had the spine of the third
vertebra of the back enlarged; in some weeks his lower extremities became
feeble, and at length quite paralytic: neither the pain of blisters, the
heat of fomentations, nor the utmost efforts of the will could produce the
least motion in these limbs; yet twice or thrice a day for many months his
feet, legs, and thighs, were affected for many minutes with forceable
stretchings, attended with the sensation of fatigue; and he at length
recovered the use of his limbs, though the spine continued protuberant. The
same circumstance is frequently seen in a less degree in the common
hemiplagia; and when this happens, I have believed repeated and strong
shocks of electricity to have been of great advantage.

4. In like manner the various organs of sense are originally excited into
motion by various external stimuli adapted to this purpose, which motions
are termed perceptions or ideas; and many of these motions during our
waking hours are excited by perpetual irritation, as those of the organs of