Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.
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Fourth. It forms a part of my views that the motive power resides in the spinal cord. The muscles furnish the instruments of power and motion. Now, there is a certain class of muscles which contract without our willing their contraction, and, gener- ally, without our being conscious that they are contracting. Such are the heart, the muscular fibres of the alimentary canal, and of the bladder, &c. These are, therefore, called involuntary muscles. There is another and larger class of muscles, which, in health, obey the bidding of the will, and serve the purposes of grasping, locomotion, and bodily effort. These are considered and called voluntary muscles. Then there is still another dis- tinct set of muscles, of which the ordinary or habitual action is involuntary, yet which do submit, also, to the occasional inter- posing control of the will. Of such are the muscles of respira- tion, which act while we are asleep, or otherwise unconscious; also of such are the sphincters, which regulate the entrances and outlets of the body. The habit of these is involuntary, but the occasional action is prompted and governed by the will. But sometimes the involuntary action rebels against the willed action, and overcomes it. The muscles contract in spite of the will. Nay, any of those muscles which ordinarily move only in obedi- ence to volition, do, sometimes, under the influence of strong emoti'on or of disease, contract independently of any effort of the will, and even in opposition to, and in defiance of, all voluntary power. It seems now fairly ascertained that the movements of those muscles which acknowledge the empire of the will, depend es- sentially upon some momentary change in the condition of the spinal cord. This change (whatever may be its nature) is capa- ble of being effected in three several ways, — 1. By volition or emotion, originating in the brain, and this sending down a nerve telegraph, which travels with electric speed to the spinal cord, whence, the requisite change having been as instantly produced, the motive influence passes, with proportional rapidity, along the nerves which connect the cord with the muscles to be moved. 2. The nervous change that is productive of motion may be