n the third; the particles of
steel on the convex side of the bent spring endeavouring to restore
themselves more powerfully the further they are drawn from each other. See
Botanic Garden, P. I. addit. Note XVIII.

I am aware that this may be explained another way, by supposing the
elasticity of the spring to depend more on the compression of the particles
on the concave side than on the extension of them on the convex side; and
by supposing the elasticity of the elastic gum to depend more on the
resistance to the lateral compression of its particles than to the
longitudinal extension of them. Nevertheless in muscular contraction, as
above observed, there appears no difference in the velocity or force of it
at its commencement or at its termination; from whence we must conclude
that animal contraction is governed by laws of its own, and not by those of
mechanics, chemistry, magnetism, or electricity.

On these accounts I do not think the experiments conclusive, which were
lately published by Galvani, Volta, and others, to shew a similitude
between the spirit of animation, which contracts the muscular fibres, and
the electric fluid. Since the electric fluid may act only as a more potent
stimulus exciting the muscular fibres into action, and not by supplying
them with a new quantity of the spirit of life. Thus in a recent hemiplegia
I have frequently observed, when the patient yawned and stretched himself,
that the paralytic limbs moved also, though they were totally disobedient
to the will. And when he was electrified by passing shocks from the
affected hand to the affected foot, a motion of the paralytic limbs was
also produced. Now as in the act of yawning the muscles of the paralytic
limbs were excited into action by the stimulus of the irksomeness of a
continued posture, and not by any additional quantity of the spirit of
life; so we may conclude, that the passage of the electric fluid, which
produced a similar effect, acted only as a stimulus, and not by supplying
any addition of sensorial power.

If nevertheless this theory should ever become established, a stimulus must
be called an eductor of vital ether; which stimulus may consist of
sensation or volition, as in the electric eel, as well as in the appulses
of external bodies; and by drawing off the charges of vital fluid may
occasion the contraction or motions of the muscular fibres, and organs of
sense.

2. The immediate effect of the action of the spirit of