Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.
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the practical laws of the voltaic pile. This is admirably illus- trated by a comparison with the Pulvamecher's chain, showing the relative value of numbers consecutively alone considered, and numbers consecutively in series, with a due proportion of sur- face, or force in each. This higher philosophic arrangement we see more nearly consummated in the electric eel. The tor- pedo fish being, as we have seen, flat and thin, the piles are necessarily perpendicular and short, reaching from its belly to its back, are very much shorter, but nearly five times more numerous consecutively than in the eel, for there are 1,880,000 diaphragms or elements, while in the Surinam eel, or gymnotus, there are only 384,000 diaphragms or elements in all. But in the eel, the animal being slim and long, the piles are laid hori- zontally, and each contains four thousand diaphragms, although there are only ninety-six series of tubes or piles. These lie from head to tail; hence less piles are required to accomplish the same object, for each pile has a relatively larger battery sur- face. The electric eel, I should have said, is some five or six feet in length, and is a more powerful fish than the torpedo, as to muscular strength. Faraday says the shock of the gymnotus, which is, by the way, a fresh-water fish, is from its natural action in the water found to be directed from its head, which is positive, to its tail, which is negative. According to De la Reve, the shock of these animals is produced only by the will; for they can discharge when they choose, but not where they choose exclu- sively, for all the water for several feet about them is at once affected. More recently, Matteucci, Savi, and Kblliker, have experi- mented with some of these fishes, and deduced many instructive facts. John Davy, brother to Sir Humphry Davy, succeeded in magnetizing steel needles, and even deviating the needle of the galvanometer, by repeatedly placing in contact with the two faces, i. e., top and bottom of the torpedo, the two extremities of a wire wound into a helix, or by employing the two platinum extremities of the galvanometer itself. He thus ascertained that the upper surface of this fish is positive, and that the lower