Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.
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wrought in the cord — whether the brain be attached to it or not — either by mechanical, chemical, or electric agencies, oper- ating directly upon the cord itself. 3. The given change that produces motion maybe wrought in the cord by an influence that is carried to the cord, and not from the brain, but from the extremities of nerves distributed upon the internal or external surfaces of the body. The action of this nervous circle, whereby, I say, an influence is first carried from the surfaces of the body along some nerves to the spinal cord, — whence, again, an influence is transmitted, or, rather, reflected, as it were, to other certain muscles along certain other nerves, — is named, by Dr. Marshall Hall, the reflex function of the spinal cord. The apparatus in our organism, that is sul>- servient to this function, is named by him the " excilo-motory system; " the nerves which cany the impression to the cord, are incident, " sentient," or excitor nerves ; those which convey the motive impulse from the cord, he calls reflex or " motor " nerves. Again, this reflex action of nerves is independent of the will; and although often attended by consciousness and sensation, yet it is often exercised when there is neither of these ; it governs the orifices by which air and food are introduced and excrements are voided. The infant breathes and nurses by it, while the adult uses his will for bringing nutriment into his mouth ; in both cases, however, after the food has reached a certain point, the act of swallowing is regulated by this same nervous function. Nevertheless, most of these muscular acts are capable of being directed, increased, or moderated by sheer voluntary will. The reflex power, on the other hand, extends, both in health and in disease, to the entire system of the strictly voluntary muscles. During health it is manifested only in the maintenance of what is called their balance or " tone;" i. e., their natural tension and firmness. In disease, on the contrary, we see this power act \ipon them sometimes with most terrific energy. There are physiologists who have said that the cerebral matter is incompressible, in consequence of the bony dome that con- tains it. This I do not believe. I am not unadvised of the other grounds upon which they rest these conclusions. Not-