up? or where are
the numerous receptacles in which those are deposited? or to what else in
the animal system have they any similitude?

That pleasing picture of objects, represented in miniature on the retina of
the eye, seems to have given rise to this illusive oratory! It was forgot
that this representation belongs rather to the laws of light, than to those
of life; and may with equal elegance be seen in the camera obscura as in
the eye; and that the picture vanishes for ever, when the object is
withdrawn.

* * * * *

SECT. IV.

LAWS OF ANIMAL CAUSATION.

I. The fibres, which constitute the muscles and organs of sense, possess a
power of contraction. The circumstances attending the exertion of this
power of CONTRACTION constitute the laws of animal motion, as the
circumstances attending the exertion of the power of ATTRACTION constitute
the laws of motion of inanimate matter.

II. The spirit of animation is the immediate cause of the contraction of
animal fibres, it resides in the brain and nerves, and is liable to general
or partial diminution or accumulation.

III. The stimulus of bodies external to the moving organ is the remote
cause of the original contractions of animal fibres.

IV. A certain quantity of stimulus produces irritation, which is an
exertion of the spirit of animation exciting the fibres into contraction.

V. A certain quantity of contraction of animal fibres, if it be perceived
at all, produces pleasure; a greater or less quantity of contraction, if it
be perceived at all, produces pain; these constitute sensation.

VI. A certain quantity of sensation produces desire or aversion; these
constitute volition.

VII. All animal motions which have occurred at the same time, or in
immediate succession, become so connected, that when one of them is
reproduced, the other has a tendency to accompany or succeed it. When
fibrous contractions succeed or accompany other fibrous contractions, the
connection is termed association; when fibrous contractions succeed
sensorial motions, the connexion is termed causation; when fibrous and
sensorial motions reciprocally introduce each other, it is termed
catenation of animal motions. All these connections are said to be produced
by habit, that is, by frequent repetition. These laws of animal causation
will be evinced by numerous facts, which occur in our daily exertions; and
will afterwards be employed to explain the more rec