[Illustration: FIG. 72.--EDISON'S ELECTRIC PEN.]
_The electric pen of Edison_, brought out in 1876 (U. S. Pat. No. 196,747, Nov. 6, 1877), is one of the simple applications of electricity, which for a number of years was in quite general use for making manifold copies of manuscript. In the illustration, Fig. 72, this is shown. It comprises a stylus _b_ reciprocated in a tube _a_ by the vibratory action of an armature _k_ over the poles of an electro-magnet, supplied with a suitable current and vibrating contacts _l h_. The stylus was rapidly reciprocated, and as the operator traced the letters on the paper, the stylus produced a continuous trail of punctures which permitted the paper to be used as a stencil to make any number of copies. It has, however, been rotated out of existence by manifolding carbon paper, and the almost universal use of the typewriter.
[Illustration: FIG. 73.--ELECTRIC CAUTERY.]
_Electricity in Medicine._--The superstitious mind is prone to resort to mysterious agencies for the cure of diseases, and for many years men of no scientific knowledge whatever have been employing this seductive instrumentality for all the ills that flesh is heir to. That it has valuable therapeutic qualities when rightly applied no intelligent person will doubt, and it is unfortunate that for the most part it has been in the hands of charlatans who sell their wares, and rely upon a faith-cure principle for the result. Still there have been intelligent experimenters in this field, and it is one of much promise for further research.
In the first century of the Christian Era (A. D. 50) Scribonius Largus relates that Athero, a freedman of Tiberius, was cured of the gout by the shocks of the torpedo or electric eel. In 1803 M. Carpue published experiments on the therapeutic action of electricity. The discovery of induction currents by Faraday in 1831 brought a new era in the medical application of electricity, in the use of what is known as the Faradaic current. The first apparatus for medical use, which operated on this principle, was made by M. Pixii in France, and the first physician who employed such currents was Dr. Neef, of Frankfort. The medical battery is a well-known and useful adjunct to the physician's outfit. Electric baths are also common and effective modes of applying the electric current. An early example of such a device is shown in the U. S. patent to Young, No. 32,332, May 14, 1861. The electric cautery and probe are also scientific and useful instruments. The cautery consists of a loop of platinum wire carried by a suitable non-conducting handle, with means for constricting the white hot loop of wire about the tumor or object to be excised. It was invented in 1846 by Crusell, of St. Petersburgh. A form of the electric cautery is shown in Fig. 73, in which _a_ is the platinum wire loop whose branches slide through guide tubes, the ends being attached to a sliding ring B. The current enters through the wire at the binding posts at the end of non-conducting handle A, and heats the platinum loop, _a_, red hot. The loop, _a_, being around the object to be excised, is constricted by drawing down the handle ring B.