A manual of practical medical electricity : the Röntgen rays and Finsen light . 29.—Diagrammatic Representation of the Area ofCuRRENT Diffusion in the Ordinary Application ofboth P:lectrodes to the Ulnar Nerve (Erb). There are four different directions of the current in the nerve. For whatever purpose we employ it, the effect it willproduce will depend largely upon the density or concentra-tion. At the points of entrance and exit of the current,this varies inversely with the size of the electrodes, andwe can accordingly increase or diminish it there as weclioose, so far as the feelings of the
A manual of practical medical electricity : the Röntgen rays and Finsen light . 29.—Diagrammatic Representation of the Area ofCuRRENT Diffusion in the Ordinary Application ofboth P:lectrodes to the Ulnar Nerve (Erb). There are four different directions of the current in the nerve. For whatever purpose we employ it, the effect it willproduce will depend largely upon the density or concentra-tion. At the points of entrance and exit of the current,this varies inversely with the size of the electrodes, andwe can accordingly increase or diminish it there as weclioose, so far as the feelings of the patient will permit ;but when once it has penetrated the surface of the body,it is no longer under strict control. Electro-Therapeutics 267 Following the law of shunts and derived circuits, thecurrent in traversing the body will pass almost entirelyby those tissues that conduct it most easily, viz., themuscles ; and it will spread out and diffuse itself in them,and in the surrounding tissues, in a way that cannot becalculated. It is therefore impossible, except by galvano-. FiG. 130.—Diagrammatic Representation of the Density andOF THE Diffusion of a Current in traversing the Trunk. The density is greatest beneath the small electrode. puncture, to insure that a certain strength of currentshould traverse a desired organ, unless the latter should bequite superficial. Fig. 129 is a diagrammatic representa-tion (from Erb) of the ordinary current diffusion in theapplication of both electrodes to the upper arm ; Fig. 130of the diffusion that may be supposed to occur when one 268 A Manual of Practical Medical Electricity electrode is applied to the nape of the neck, and the otherforms the patients seat. It will be noticed that thecurrent is much densest beneath the electrodes, and thatthough it passes mainly in the direct line between them,yet that there are diffusion currents passing down the armsand thighs. If it be a mere question of passing a currentof a given strength throug
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