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

sulatcd, and communicating only by the conductors of the gal- vanometer, and prepared with every precaution, so as to be de- prived of all electro-motive force whatever. Then, when the needle has become tranquil, he contracts all the muscles of one arm as powerfully as possible, at the same time taking care to avoid the least movement of the other arm and fingers. At the moment of contraction the galvanometer shows an impulse, the intensity of which depends upon the strength of the subject and the adroitness of the operation ; but the invariable direction of the current travelling in the contracted arm is from the hand towards the shoulder. This reverse direction of the animal electric current he thinks can only bo attributed to the diminution or exhaustion, or nega- tive variation, as it is called, that is suffered by the native mus- cle electric current, and produced simply by the contraction of the arm; whence it is inferred that the natural current in the arm that was kept at rest preponderates; for before the trial, their respective animal currents balanced each other, because of their similarity. The natural animal electric current, however, of the human arms, during life and health, travels, in each of them, in the direction from the shoulder to the hand; i. e., from the nerve centres to the periphery and extremities. It has been clearly demonstrated by Dubois-Rcymond, aided by his exquisite Galvanometer-multiplier, that there exist in the nerves, as in the muscles, of man, perfectly determinate currents of animal electricity. This is as true of all the nerves as of the living muscles, whatever their respective functions, as well in the nerves of sensation as in the nerves of motion, in the ante- rior as in the posterior root, and in the mixed nervous centres as in those that are simple. The nerves of man and of animals in this respect present the same phenomena, and are subject to the same laws, as the currents in living muscles. The latter are supposed to be only the effect of the electric polarity of the \iltimate nervous partitions, and of the arrangements which they assume under the all-controlling influence of the undefinable vital force. Says a distinguished philosopher, it would be intensely inter-