and induced
by natural or artificial stimuli, or in a diminished excitement or
debility in the whole, or in part. It likewise teaches us that the
natural and only efficacious cure of these diseases depends on the
abstraction of stimuli, from the whole, or from a part of the body,
when the excitement is in excess: and in the increase of their number
and force when the contrary takes place.

The light which the discoveries of Galvani, and others who have
followed his steps, begin to throw on physiology, promises, when
aided by the principles of chemistry, and the knowledge of the laws
of life, to produce all the advantages that would result from a
perfect knowledge of the animal functions.

From what has been said, it does not seem improbable that muscular
contraction may depend upon the combination of oxygen with hydrogen
and azote, in consequence of a sort of explosion or discharge
produced by nervous electricity. According to this hypothesis, animal
motion, at least that of animals analogous to man, would be produced
by a beautiful pneumatic structure. This hypothesis, though not
perhaps at this moment capable of strict demonstration, seems
extremely probable, it being countenanced by every observation and
experiment yet made on the subject. It accounts likewise for the
perpetual necessity of inhaling oxygen, and enables us to trace the
changes which this substance undergoes, from the moment it is
received into the system, till the moment it is expelled. By the
lungs it is imparted to the blood; by the blood to the muscular
fibres; in these, during their contraction, it combines with the
hydrogen, and perhaps carbon and azote, to form water and various
salts, which are taken up by the absorbents, and afterwards exhaled
or excreted. We know the necessity of oxygen to muscular motion, and
likewise that this motion languishes when there is a deficiency of
the principle, as in sea scurvy. Thus a boundless region of discovery
seems to be opening to our view: the science of philosophy, which
began with remote objects, now promises to unfold to us the more
difficult and more interesting knowledge of ourselves. Should this
kind of knowledge ever become a part of general education, then the
causes of many diseases being known, and the manner in which the
external powers, with which we are surrounded, act upon us, a great
improvement not only in health, but in morality must be the
consequence.

With respect to its influenc