The medical application of electro-magnetism / by Samuel B. Smith.
- Smith, Samuel B., approximately 1794-
- Date:
- 1853 [©1850]
Licence: Public Domain Mark
Credit: The medical application of electro-magnetism / by Samuel B. Smith. Source: Wellcome Collection.
Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.
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![ft solution of isinglass. 'I'lie injection i.s of an intense color, perfectly fluid, Mud is thus enable,] to penetrate the minutest raniifications of the capillary vessels. In injecting the brain, it is nece^sn-y to use (jiic that is pi'ifeetly fi-esh ; and i generally inject immediately after tiie anim il is killed. By these means, the most exquisite injections of tlio brain anri spinal ch(jrd have l)een e.xecuted ; and, in all my prepara- tions, it is shown that wherever the <£iev matter exists, the blood is disti'ibuted, and where tiie wliite m itter exists, there is no blood ; and, upon these considerations, physiologists infer that the grey matter ia the active p irt of the b.'aiu.—Eleiu. Electro-Biol. p. 30. AN EXPERIMENT ILLUSTRATIVE OF THE N E G A r I V E AND POSITIVE E L E C T l{ I C P O W p; R. The apparatus required for the peiformance of this experiment, are an electric macliine, a small Leyden jar, a Hat cake of pitch, a small tin can witli a glass stem for insulation, and a spring puff or bag, con- taining a mixture of sulphur and red lead. Tlie resinous cake being quite dry and free from dust, I place the little can upon it at some short distance from the middle of the suiface. 1 tiien electrize the inside of tiie jar negatively, either by placing its knob in connexion with the negative conductor of the maciiine, or by holding its outer coating agiinst the positive conducior: (the for- mer way is preferable, because the liand has already hold of the body of the jar) which done, I present its ball to the can, from which it recovers a small quantity of its lost fluid. The can, consequently, becomes electro-negacive, and its rim, in connection with the resinous cake, rendei'B a ring of the latter also negative. I now lift up the can by its glbs handle, and, for a moment, touch it with my linger to restore its electric equilibrium. The can is then placed on another part of the resinous surface, the jar discharged, and again recharged with its ball at the prime conducto.-. A spark is now transmitted f;om the ball of the jar to the cm, which renders it elec- tro-positive; and a considerable portion of this charge is transmitted to the resinous cake, spreading outward by its repuLive attribute, on every side of the can ; and, when the latter is removed by its glass handle, tiie electric fluid advances inward also, until the forces on op- posite sides of the centre, balance one another, and completely a.-rest the fluid's further advance. Tiie c ike, being thus differently electrized on two parts of its sur- face, is then placed in a ve. tical position, and then standing at a con- sideral)ie distance, L project towards it the mixed powders from the spring bag, which, whilst traversing the air between the bag and the elfctrized surfaces, become influenced by the latter and attracted by them, according to the strict principles of electric ao'.ion : the sulphur attacliing itself to the positive suifice, and the red lead to the nega- tive one. 'i'iie beauty of this exp-riment is beyond all desciiption, and, in a theoretical point of view, in one of the highest importance. Nothing](https://iiif.wellcomecollection.org/image/b21078373_0031.jp2/full/800%2C/0/default.jpg)
