The medical and surgical uses of electricity, including the X-ray, Finsen light, vibratory therapeutics, and high-frequency currents / by A. D. Rockwell ... with two hundred and fifty-two illustrations.

Date:
1903
Catalogue details

Licence: In copyright

Credit: The medical and surgical uses of electricity, including the X-ray, Finsen light, vibratory therapeutics, and high-frequency currents / by A. D. Rockwell ... with two hundred and fifty-two illustrations. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    same, than large, broad electrodes. Hence, except in those cases where it is desired to confine the action of the current to a very limited surface, electrodes of pretty good surface are desirable. Electrophorus.—The electrophorus, invented by Volta in 1775, consists of a metallic mould, filled with a mixture of shellac and turpentine, and a movable metallic cover that is provided with a glass handle. The sur- face of the shellac is negatively electrified by beating it with a cat’s fur or fox-tail. The cover is then put on, and by contact becomes negatively electrified, and gives to the finger a slight spark of negative electricity. If the cover be now removed by its insulating handle, it gives positive electricity to w'hatever touches it. This positive electricity it acquires not directly from the shellac, but by inductive action through the air. Fig. 7. Electric Machmcs.—T\\\s term is exceedingly vague. It is applied to any and all forms of electrical apparatus. The first electric machine was made in 1672, by Otto von Guericke, of Magdeburg.* It consisted of a globe of sulphur, turned on its axis by one hand and pressed against the other hand. Afterward a glass cylinder was used instead of sulphur. In 1740 Winckler substituted cushions of horsehair as rubbers. In 1760 Ramsden substituted a circular glass plate for the glass cylinder. The forms of electric machines now used are modifications of Ramsden’s. This is one of the forms of apparatus from which we obtain static elec- tricity. Fig. 8 represents the common cylinder electric machine, for de- veloping electricity by friction. Jnjl7mice Machmes.—These machines differ from that just described in that they depend upon the principle of influence and the principle of re- ciprocal accumulation. Let there be two insulated conductors {A and B, Fig. 9), electrified ever so little, one positively, the other negatively. Let a third insulated conductor (C), which will be called a carrier, be arranged * “ Experimenta Nova,” Magcleburgica.