Zoonomia, Vol. I | Page 5

change in them, are carried forward into the
blood, and supply perpetual nourishment to the system, or replace its
hourly waste.
8. The stomach and intestinal canal have a constant vermicular motion,
which carries forwards their contents, after the lacteals have drank up
the chyle from them; and which is excited into action by the stimulus of
the aliment we swallow, but which becomes occasionally inverted or
retrograde, as in vomiting, and in the iliac passion.
II. 1. The word sensorium in the following pages is designed to express
not only the medullary part of the brain, spinal marrow, nerves, organs
of sense, and of the muscles; but also at the same time that living
principle, or spirit of animation, which resides throughout the body,
without being cognizable to our senses, except by its effects. The
changes which occasionally take place in the sensorium, as during the
exertions of volition, or the sensations of pleasure or pain, are termed
sensorial motions.
2. The similarity of the texture of the brain to that of the pancreas, and
some other glands of the body, has induced the inquirers into this
subject to believe, that a fluid, perhaps much more subtile than the
electric aura, is separated from the blood by that organ for the purposes
of motion and sensation. When we recollect, that the electric fluid itself
is actually accumulated and given out voluntarily by the torpedo and
the gymnotus electricus, that an electric shock will frequently stimulate
into motion a paralytic limb, and lastly that it needs no perceptible
tubes to convey it, this opinion seems not without probability; and the
singular figure of the brain and nervous system seems well adapted to
distribute it over every part of the body.
For the medullary substance of the brain not only occupies the cavities
of the head and spine, but passes along the innumerable ramifications
of the nerves to the various muscles and organs of sense. In these it lays
aside its coverings, and is intermixed with the slender fibres, which
constitute those muscles and organs of sense. Thus all these distant

ramifications of the sensorium are united at one of their extremities,
that is, in the head and spine; and thus these central parts of the
sensorium constitute a communication between all the organs of sense
and muscles.
3. A nerve is a continuation of the medullary substance of the brain
from the head or spine towards the other parts of the body, wrapped in
its proper membrane.
4. The muscular fibres are moving organs intermixed with that
medullary substance, which is continued along the nerves, as
mentioned above. They are indued with the power of contraction, and
are again elongated either by antagonist muscles, by circulating fluids,
or by elastic ligaments. So the muscles on one side of the forearm bend
the fingers by means of their tendons, and those on the other side of the
fore-arm extend them again. The arteries are distended by the
circulating blood; and in the necks of quadrupeds there is a strong
elastic ligament, which assists the muscles, which elevate the head, to
keep it in its horizontal position, and to raise it after it has been
depressed.
5. The immediate organs of sense consist in like manner of moving
fibres enveloped in the medullary substance above mentioned; and are
erroneously supposed to be simply an expansion of the nervous
medulla, as the retina of the eye, and the rete mucosum of the skin,
which are the immediate organs of vision, and of touch. Hence when
we speak of the contractions of the fibrous parts of the body, we shall
mean both the contractions of the muscles, and those of the immediate
organs of sense. These fibrous motions are thus distinguished from the
sensorial motions above mentioned.
6. The external organs of sense are the coverings of the immediate
organs of sense, and are mechanically adapted for the reception or
transmission of peculiar bodies, or of their qualities, as the cornea and
humours of the eye, the tympanum of the ear, the cuticle of the finders
and tongue.
7. The word idea has various meanings in the writers of metaphysic: it

is here used simply for those notions of external things, which our
organs of sense bring us acquainted with originally; and is defined a
contraction, or motion, or configuration, of the fibres, which constitute
the immediate organ of sense; which will be explained at large in
another part of the work. Synonymous with the word idea, we shall
sometimes use the words sensual motion in contradistinction to
muscular motion.
8. The word perception includes both the action of the organ of sense in
consequence of the impact of external objects, and our attention to that
action; that is, it expresses both the motion of the