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In supposing a principle of life in nerves, similar to what is conceived to exist in muscles, we might naturally expect to find certain analogies of func tions in those organs. The facility, celerity, and accuracy of the nervous actions, seem like those of the muscles to be improved by use; as is exemplified in the quick and correct perceptions of those who are accustomed to exercise their auditory nerves in attending to musical sounds. A train of nervous actions having often taken place they, like similar actions in muscles, become concatenated, and are liable to occur in succession, when one of them is accidentally induced. Both nerves and muscles require temporary respites from action, and are refreshed by sleep.

The supposition of actions occurring in the nerves, explains many circum

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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

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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