Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.
329/740

Polar-working of either the primary or secondary current is a term given to whatever effects are produced at the site of the two electrodes, at the entrance, during the stay, and at the leaving of the current. This term, tlierefore, covers those older terms of " convulsion pole," " painful pole," and also those changes which were produced, or rather were supposed might be produced, by a protracted application of the electrode in the same spot. Grapengeisser, Matteucci, and Remak, particularly, state that the action of the zinc pole of the constant or primary current, as of Daniell's battery, is the strongest. We find that the down- running of such a current produces stronger twitching at the closure of the circuit, during the closure, and at the moment of taking it away; while the up-running current produces more twitchings and longer enduring contractions, both at the making and breaking of the current. This rule applies not only to the superficial nerves at the borders and surface of the muscles, — as this can be distinctly seen by trials on the muscle biceps,— but it applies also to the deeper ramification of the motor nerves, even those situated deep inside the body of the muscle. Intro-polar workings of electric currents arc those which become apparent, even in healthy persons, in the territory of the ultimate ramifications of a nerve that is being embraced in the electric current; as, for example, where the current has been applied and maintained in the contrary direction to the natural nerve- current ; and thus a modification in the latter is produced. Extra-polar working of a current is simply that which is pro- duced outside of the direct route between the two electrodes, and which is manifested by sensations or motions not properly arising through the nerve fibrils embraced by the current. These effects are more easily traced in sentient than in motory nerves. Under this head we will call attention to the fact that any one can observe, viz., that when employing strong induction cur- rents, as upon the nerves and muscles of the arm, if the elec- trodes are pressed hard upon or over the motor nerve, it lessens the pain, and at the same time causes the contractions to take place stronger and deeper. This is a strange phenomenon. It