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!!!!1878 __ D’Arsonval galvanometer & galvanoscope * Jacques Arsène d’Arsonval (1851-1940) * ''Translated excerpt :'' « I prepared a frog in Galvani’s manner. I took Siemens’s instrument of induction, used in physiology under the name of the chariot instrument. I excited with the ordinary pincers the sciatic nerve, and I withdrew the induced coil until the nerve no longer responded to the electric excitement. I then substituted the telephone for the nerve, and the induced current, which had ceased to excite the latter, made the instrument vibrate strongly. I withdrew the induced coil, and the telephone continued to vibrate. In the stillness of the night I could hear the vibration of the telephone when the induced coil was at a distance fifteen times greater than the mnimum at which the excitement of the nerve took place ; consequently, if the same law of inverse squares applies to induction and to distance, it is evident that the sensitiveness of the telphone is two hundred times greater than that of the nerve. The sensitiveness of the telephone is indeed exquisite. We see how much it exceeds that of the galvanoscopic frog’s leg, and I have thought of employing it as a galvanoscope. It is very difficult to study the muscular and nervous currents with a galavanometer of 30,000 turns, because the instrument is deficient in instantaneous action, and the needle, on account of its inertia, cannot display the rapid succession of electric variations, such as are effected, for example, in a muscle thrown into electric convulsion. The telephone is free from this inconvenience, and it responds by vibration to each electric change, however rapid it may be. The instrument is, therefore, well adapted for the study of electric tetanus in the muscle. It is certain that the msucular current will excite the telephone, since this current excites the nerve, which is less sensitive than the telephone. But for this purpose some special arrangement of the instrument is required. It is true that the telephone can only reveal the variations of an electric current, however faint they may be ; but I have been able, by the use of very simple expedient, to reveal by its means the presence of a continuous current, also of extreme faintness. I send the current in question into the telephone, and, to obtain its variations, I break this current mechanically with a tuning-fork. If no current is traversing the telephone, it remains silent. If, on the other hand, the faintest curent exists, the telephone vibrates in unison with the tuning-fork. » ''(D’Arsonval, research account in the records of the Académie des Sciences, April 1st, 1878, In Theodore du Moncel, “The telephone, the microphone, and the Phonograph”, pp. 136-138, 1879, Ayer Publishing, 1974)'' * ''Attached references :'' {small}Don Francisco Salva y Campillo (1751-1828), ''Wireless telegraphy using freshly severed frogs' legs'' (1798).{/small} * ''Sources :'' {small}J. A. D’Arsonval. (1879). ''Les nouvelles applications et les perfectionnements du téléphone''. In ‘Revue scientifique’, 1879, 1: pp. 200-212 ; Th. du Moncel. (1879). ''The Telephone, the Microphone, and the Phonograph''. pp. 136-138. {/small} {br}{br}
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