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

from the one-way passage of any electric current. This polari- zation simply consists in the fact that the molecules of the nerves, naturally endowed, as they are, like those of the muscles, with two electricities, turn all their positive poles towards, or with the way the foreign voltaic current is going, while all their negative poles are towards from whence it comes. The mole- cules of the nerves are supposed to be bi-polar, and arranged as in muscles and other fibre. This explains the manifestation of the nervous current, which is in the same direction with the muscular current. But under the influence of the exterior vol- taic current, the nerve molecules being more mobile than muscle molecules, they arrange themselves, one after the other, accord- ing to the true mode of polarization. This condition is assumed even in portions or branches of the living nerves that are trav- ersed where these twigs are not directly traversed through by the current. This action is called extra-polar working-, and has a tremendous bearing, as we shall have occasion to observe, on the every-day results obtained in systematic electro-medical practice. There is obtained from these microscopic results and philo- sophic deductions a law that there results, from a foreign or gal- vanic steady current actually coursing for a given time through a nerve trunk, " an abiding influence" which causes an increase or diminution of the active native electro-nerve current, and that according as the artificial current was made to bear upon the nerve, whether directed against or with the native current — whether often or seldom reversed or repeated, or long continued. Again : if the nerve is placed between two clean platinum plates which serve as the poles of a very gentle but finely inteiv ruptcd induction current, and hence alternating in rapid oppo- site directions and in regular succession, there is a tetanization produced. On suspending this artificial current, after a short time we see that the galvanometer indicates a decided diminu- tion in the nerve current proper in that living part, whatever may be the so-called direction of this exterior current; whilst, with the continuous and even stream of galvanism, continued for the same length of time, we get an increase in the living 17