File:General physiology of muscles and nerves (1881) (14591016459).jpg

Identifier: generalphysiolo00rose (find matches)
Title: General physiology of muscles and nerves
Year: 1881 (1880s)
Authors: Rosenthal, I. (Isidor), 1836-1915
Subjects: Physiology Muscles Nerves
Publisher: New York, D. Appleton and company
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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be shown by means of an electrometer, ifthe latter is brought into contact with each point inthe wire. The gradual decrease of the tensions in thewire is evidently also the essential cause of the move-ment of the electricity through the wire, for at eachpoint in the wire there are adjacent portions in whichthe tensions gradually become less from left to right,so that the electricity is enabled to flow from left toright. The case is evidently like that of a tube through ELECTRIC FALL. 173 which water flows, for in that case also the pressure ofthe water gradually and regularly decreases from oneend to the other. To express this similarity we willapply to electric currents a term borrowed from flowingliquids, and will call the gradual decrease in the tensionthe fall ill. the electricity. Let us compare two wires of the same thickness,but of unequal length, a b and c d (fig. 42). If a bis inserted between the poles of a chain, the fall isrepresented by the oblique line e f. Supposing a b
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Fig. 42. The electric fall ix uiFFEiiEXT wires. removed, and c d inserted between the poles of thesame chain, the tensions at the ends would be the same,so that the fall in the ease of the wire c d may berepresented by the oblique line rj h. It will be ob-served that in the case of the shorter wire the line runsmuch more abruptly, the fall is greater, and the cur-rent of electricity advances much more rapidly in thiswire. Assuming now that the two wires a b and c dare simultaneously attached to the poles of the chain,in this case also the tensions at the two ends must beequal, but the fall must be different. Supposing that 174 PHYSIOLOGY OF MUSCLES AND NERVES. instead of these two wires a number of separate wiresare used, then the same thing happens; and if the wiresare welded together into a common conducting body,this does not essentially alter the conditions of the fall,so that we may imagine the whole body to consist ofthese separate wires, in each of which a definite fall,the ste

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