OBSERVATIONS ON IRRITABILITY. 289
perform not only involuntary motions when ftimulated, but, in ap¬
pearance, alfo voluntary ones. In like manner, the body of a frog,
after being divided from the head, preferves the power of motion for
above an hour ; and when its hind feet or toes are cut, or otherwife
hurt, the mufcles of its thighs, legs, and trunk are ftrongly con¬
tracted, by which it raifes its body from the table, and fometimes
moves from one place to another. When the mufcles of the thighs
are pricked or cut with a knife, they are excited into contradion ;
but neither they, nor the neighbouring mufcles, are near fo ftrong¬
ly convulfed as when the toes are wounded. Whence fhould this
happen ; and why fhould not the mufcles of the legs and thighs be
more ftrongly convulfed, when they themfelves are wounded, than
when the toes are treated in the fame manner ? This would be the
cafe, if the motions of irritated mufcles were owing to fome pro¬
perty of the infenfible matter compofing them. But if, as we ima¬
gine, they are all to be derived from feeling, it is eafy to fee, that, as
the feet and toes are more fenfible of pain when wounded, than the
mufcles of the legs or thighs, ftronger convulfions muft be occa-
fioned by an irritation of the former than of the latter.
Further, we muft either allow that both the head and body
of a frog continue to be animated for fome time after they are fe-
parated from each other; or elfe affirm, that the life, feeling, and
a clive powers of animals, are merely properties of that kind of mat¬
ter of which they are made. The former opinion is attended with
fome difficulties, which arife chiefly from our ignorance of the na¬
ture of immaterial beings : the latter feems to be inconfiftent with
ail the known properties of matter. If the latter therefore be ad¬
mitted, we not only afcribe qualities to matter^hich it does not
poffefs, but prefume to limit, by our narrow and inadequate capa¬
cities, the powers of incorporeal natures, their manner of ading
upon bodies, and co-exifting with them.
If the foul were confined to the brain, as many have believed *9
whence is it that a pigeon not only lives for lèverai hours after be-
mg deprived of its brain, but alfo flies from one place to another
O 0 And
f Baglivi opera, 4to, pr&fat. p. n. '
# Aft, Gotting, vol. 2. p. 153.