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ture. Thus we seem to be acquainted with the properties of the aggregate forms of that substance which is cognizable to the eye and touch, and which we then call matter; we seem to be assured of the existence, and to know something of the properties, of a subtile substance which pervades all nature; and if we are allowed to know any thing, we surely may be admitted to know the properties of our own minds.

How diversified are our perceptions, how admirably are they adapted to our wants and gratifications! for all beauty of prospect, all melody of sound, all variety of odour, must by the eye of reason be perceived to result from the masses or molecules of surrounding matter, being in various states of motion or of rest; of which circumstances we have notice by the actions they induce in our ner

vous fibrils. Such variety of perceptions I can only consider as the effect of the peculiar properties of that which feels, remembers, reasons, and wills, and which seems connected with the brain alone.

The conclusion to be drawn from this examination of the functions of the nervous system is curious and interesting. We perceive an exact correspondence between those opinions which result from physiological researches, and those which so naturally arise from the suggestions of reason that some have considered them as intuitive. For most reflecting persons in all ages have believed, and indeed it seems natural to believe, what modern physiology also appears to teach, that in the human body there exists an assemblage of organs, formed of common inert matter, such as we see after death, a principle of life and action, and a sen

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stances connected with diseases. Vehe-. ment actions may occur in the tangible extremities of nerves, independent of impulses, and occasion severe pain. This seems to happen in the disease called tic douloureux. Ordinarily, actions beginning in the tangible extremities of nerves, are regularly transmitted to the brain; but in cases of nervous pains, actions sometimes seem to begin in the middle of nerves; and it is probable, that actions beginning in the sensorial extremities of nerves may be productive of illusory sensations, and excite fallacious ideas.

If this theory of nervous actions could be proved, the extent of our knowledge would only lead to this conclusion, that motions of a subtile substance, propagated to and fro in the nervous fibrils, took place in consequence of excitement by

impulses and volition; but from such motions it seems impossible to account for sensation or volition. We can conceive no variety in these motions, but what relates to degree, duration, and succession, and it seems impossible to believe that sensation can be the result of such motions, or that ideas can arise from any succession or train of them. Certain persons will therefore I doubt not continue to think that sensation, remembrance, comparison, judgment, and volition, are properties of some distinct substance.

The essences or primitive parts of what we call matter, are too subtile to be perceived by our senses, and seem even to elude our conceptions. Is it not then most philosophical to acknowledge our ignorance on these points, and to speak of what we do know, the properties of the different species of substances in na

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stances connected with diseases. Vehe-. ment actions may occur in the tangible extremities of nerves, independent of impulses, and occasion severe pain. This seems to happen in the disease called tic douloureux. Ordinarily, actions beginning in the tangible extremities of nerves, are regularly transmitted to the brain; but in cases of nervous pains, actions sometimes seem to begin in the middle of nerves; and it is probable, that actions beginning in the sensorial extremities of nerves may be productive of illusory sensations, and excite fallacious ideas.

If this theory of nervous actions could be proved, the extent of our knowledge would only lead to this conclusion, that motions of a subtile substance, propagated to and fro in the nervous fibrils, took place in consequence of excitement by

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