Electricity in its relations to practical medicine / by Moritz Meyer.

  • Meyer, Moritz, 1821-1893.
Date:
1874, ©1869
Catalogue details

Licence: Public Domain Mark

Credit: Electricity in its relations to practical medicine / by Moritz Meyer. Source: Wellcome Collection.

Provider: This material has been provided by the Harvey Cushing/John Hay Whitney Medical Library at Yale University, through the Medical Heritage Library. The original may be consulted at the Harvey Cushing/John Hay Whitney Medical Library at Yale University.

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    negative metal. In the conducting fluid the current always goes in the contrary direction, that is, from the zinc through the fluid to the copper. In every open battery, no matter whether simple or compound, each pole has free electricity of a certain tension, the quantity of which is equal at each pole. At the positive pole it is represented by +, at the negative pole by —. The tension increases with the num- ber of the elements in arithmetical progression, so that in the middle of the pile, at the so-called neutral point, there is a pair of plates that have no free electricity, and by which the pile is divided into two equal opposing halves. If the current is conducted by means of a straight wire, parallel with and over or under a magnetic needle, the needle will deviate in proportion to the number of the elements. The direction of the deviation is variable, depending upon the current being conducted over or under the magnetic needle, or whether the direction of the current be changed or not. In order to determine the direction of the current from the position of the needle, the following rule of Am- pere is used: Imagine to yourself a human figure, intro- duced into the current so that it enters at the feet and goes out at the head. If the figure turns its face toward the needle, the north pole of the needle will always be turned toward the left of the figure. By this rule we see that the several parts of the current which is led in a circle around a needle all tend in like manner to make the needle deviate, and also to mutually strengthen one another. In order, therefore, to produce an observable deviation, it is only ne- cessary to have a greater number of well-isolated coils of the wire in a parallel direction. Such an instrument, which serves to recognize weak currents, and to determine their direction, is called a multiplicator, and may be used as a galvanometer. If we turn now to the action of the electrical currents, we must recognize two distinct series of them, the one going on in the conducting body itself, the other in the distance— 2