Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.
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ring to the action of the current in the living- body, lie says, " Only within certain limits, the definition of which would be difficult, does the continuous working of the current on the organs become at rest; for the minute shocks, or blows, which are like rapidly repeated sparks, following one another almost, if not quite, without interruption, in some way or another min- gle into one single prolonged blow, as, indeed, I have hereto- fore tried to explain." In the above quoted passage, evidently Volta advances the idea that the contact, or first flow of a current from a closed circuit of a voltaic pile, consisting say of one hundred pairs, is not simply and absolutely one blow or shock, but is an impres- sion made as one out of one hundred blows or shocks, which follow each other so rapidly, yet in actual succession, that they mingle together as one shock. Another instructive deduction of Volta's, in this connection, is found in the following: " What applies in effect from the action of the voltaic current, to the sensitive parts of the body, does not also in like manner apply to those endowed only with irritability. The muscle, for instance, shows only a quick or instantaneous together-drawing (when either touched itself directly, or through its nerve by the current) at the instant of contact, or closure of the chain, which is sometimes also observed at the opening or breaking of the chain, and which is the reason that the chain must be now and then opened and closed, if we wish to produce sensible action in contractions. But this must not lead us to suppose, that the closed current which flows quietly and imperceptibly on through the muscles and their nerves, is not affecting them ; for they do become, from a long-continued action of the current, on the contrary, in some degree or sense paralyzed, although they appear to be in no way changed, nor even disturbed in structure." In a letter to the Right Honorable Sir Joseph Banks, which is found recorded in the Philosophical Transactions, London, 1800, Dr. Yolta says, that when he introduced the poles of a pile of thirty to forty pairs into the external opening of his own ear, he felt a shock to his head, and some moments afterwards