Electro-therapeutics, or, Electricity in its relation to medicine and surgery.

  • King, William Harvey, 1861-1942.
Date:
[1889], [©1889]
Catalogue details

Licence: Public Domain Mark

Credit: Electro-therapeutics, or, Electricity in its relation to medicine and surgery. 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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    keep the current on the patient only during the regular treat- ments by substitution, and for this method of measurement the switch-board has special devices. After getting the deflec- tion of twenty milliamperes, as in the first case, by any suitable number of cells, by simply turning a switch, the patient is cut out of the circuit and the rheostat substituted for the patient. It now simply becomes necessary to throw into the circuit suffi- cient resistance to produce the same deflection as was pro- duced by the resistance of the patient, when the resistance must equal that of the patient. It will be observed that the same law of the ratio of resistance to current with a constant electro-motive force holds true here, and the substituted resistance, which is a known resistance, equals that of the patient, because the current is the same in both cases. It must be remembered that the number of cells in use during the treatment of the patient and the observation with the rheostat must be the same. This key-board also contains a faradic battery with the coils of the Du Bois-Reymond pattern and of the Engleman dimensions, and will be described further on. Fig. 9 represents a cabinet battery with the same key- board. Milliampere Meter.—It becomes necessary to speak of the accessories wanted in connection with the use of a galvanic current, and we must place the milliampere meter at the head of the list, as it is as important as the graduate and balance of the apothecary, and, indeed, we may say no accurate or repeated dosage or treatment can be given electrically without it. A milliampere meter is a galvanometer, whose deflections have a definite value, and may be called a graded or absolute galvanometer. We may now refer to our original figure again, and remember that on the wire being placed in the ends of the zinc and copper plates, we observed that it became warm and that it deflected the needle suspended over it to the right or east. If the wire, instead of passing under the needle, passes over it, the deflection will be greater, and if the wire be made into a coil, the deflection will be still greater. Such a coil with a needle suspended within it is called a multiplier, on account of the added or accumulative effect of each additional coil or spiral of wire. By placing a