The experimental method in medical science : second course of the Cartwright Lectures of the Alumni Association, College of Physicians and Surgeons, New York delivered January 24, January 31, and February 7, 1882 / by John C. Dalton.

  • Dalton, John Call, 1825-1889.
Date:
1882
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Licence: Public Domain Mark

Credit: The experimental method in medical science : second course of the Cartwright Lectures of the Alumni Association, College of Physicians and Surgeons, New York delivered January 24, January 31, and February 7, 1882 / by John C. Dalton. Source: Wellcome Collection.

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    they were first made is a topic of much interest.1 He was in his laboratory, engaged on experiments with the electrical machine, and had, lying upon the table near by, a freshly dissected frog, prepared for some other purpose in such a way that the denuded hind legs were connected with the spinal column by the crural nerves. One of his assistants, accidentally touching the nerves of the animal with the blade of a scalpel, saw the legs convulsed; and, on watching more closely, it was seen that the contraction occurred only at the moment of drawing a spark from the conductor of the machine. Once Galvani’s attention at- tracted to so remarkable a phenomenon, his mind turned instantly to the investigation of its conditions. He abandoned all other occupations, and seemed absorbed in the attempt to detect its causes, and to learn their mode of operation. He determined, in the first place, that the discharge of the conductor, and the contact of the scalpel with the frog’s nerves, were both necessary; for the mus- cular contraction would not take place with either of them alone. But, even when both conditions were present, sometimes the muscles contracted, and sometimes they did not. Puzzled by this variation, but still confident that it must have a reasonable cause, he at last found that it depended on the way the scalpel was held in the fingers. If grasped by the end of its non-conducting ivory handle, there were no convulsions in the legs when the spark was taken from the machine; but if held in' such a way that the fingers touched the steel blade, or the rivets which held it in place, the muscles were always thrown into action. The human body, therefore, served as a con- 1 Aloysii Galvani de Viribus Electricitatis in Motu Musculari Commentarius. De Bononiensi Scientiarum et Artiura Instituto atque Academia Commentarii, 1791. Tomus septimus, p. 363.