Electro-therapy in gynæcology / by Samuel Sloan.

  • Sloan, Samuel, 1843-1920.
Date:
[1917]
Catalogue details

Licence: Public Domain Mark

Credit: Electro-therapy in gynæcology / by Samuel Sloan. Source: Wellcome Collection.

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    negative plate. Various devices are resorted to in order to counteract polarisation and so keep the voltage, and consequently the current, steadier. In the Leclanche cell (see Fig. 9, p. 59) binoxide of manganese is employed for this purpose ; being mixed with powdered carbon and placed in a porous pit, the contents acting as a carbon plate. In the galvanic cautery cells bichromate of potash and chromic acid are employed to serve this purpose. The action of these de-polarisers is to supply oxygen to the evolved hydrogen deposited on the negative plate of the cell, and thus remove it. The physical effects of the current are mainly magnetic, thermic and electrolytic. The magnetic effect is shown in the fact that a wire carrying the current is able to deflect the needle of a mariner’s compass, if the wire through which the current is passing be held over or under the magnetised needle ; the direction of the current determining the direction towards which the needle will be deflected. When we speak of the direction of the current it is conventionally understood that the current flows, outside the cell, from the positive pole to the negative pole; whilst inside the cell it is flowing from the positive to the negative plate (see p. 17). In reality, however, as has been shown, a current is flowing in both directions. Heat is always generated in an electric circuit, the amount being proportional to the product of the square of the current into the resistance. As was seen to be the case with static electricity, so is it with electricity in motion. Through some con¬ ductors the current passes with very little difficulty— silver and copper, for instance, if pure and moderately thick, have extremely little resistance; whilst others, such as platinum and the element carbon, especially if of a very small cross section, cause a very considerable amount of resistance, and therefore of heat. This property, in the case of the platinum, is utilised in the galvanic cautery; whilst carbon is employed as graphite
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