Electro-physiology (1896-98) Electro-physiology electrophysiolog02bied Year: 1896-98 306 ELECTRO-PHYSIOLOGY CHAP. nerve, extends not merely to equality of an- and katelectrotonic deflections, but also to the more or less approximate proportion which exists at a given position of leading-in and galvanometer electrodes, between the magnitude of effect produced and intensity of the polarising current (38). An essential characteristic of ' electrotonic ' currents, as opposed to ordinary current escape, is presented by the fact that the direction of the extrapolar current led off is determined by
Electro-physiology (1896-98) Electro-physiology electrophysiolog02bied Year: 1896-98 306 ELECTRO-PHYSIOLOGY CHAP. nerve, extends not merely to equality of an- and katelectrotonic deflections, but also to the more or less approximate proportion which exists at a given position of leading-in and galvanometer electrodes, between the magnitude of effect produced and intensity of the polarising current (38). An essential characteristic of ' electrotonic ' currents, as opposed to ordinary current escape, is presented by the fact that the direction of the extrapolar current led off is determined by the position of the galvanometer (t 772 + •I- ! FIG. 217.—Schema of current diffusion in an ordinary conductor partially traversed by current. FIG. 21S.—Schema of current diffusion in a 'core-model.' (Griinhagen.) current. This is shown by the accompanying schema (Fig. 217), where it is seen that the extrapolar branches of current led off from opposite sides of the conductor must necessarily be hetero- dromous. On the other hand, this does not occur either in the nerve or in any of the models described above. Whatever the position of the galvanometer electrodes, the current led off is invari- ably homodromous with the polarising current. The sole essential condition is that the axis of a moist conductor should contain a core of letter conductivity than the sheath. It is immaterial whether, as in
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