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

cles, the polarization of the nerve must take place in the oppo- site direction ; so that the positive poles of all the molecules are turned towards the nerve centres, while the negative poles are towards the muscles from whence the excitation came. Hence a galvanic current run towards the brain produces more sensa- tion, but, when down-running, — i. e., from the brain, — more contraction. Polarization is therefore established in a contrary direction in a nerve of motion and in a nerve of sensation. The exception is where a compound nerve is tested with an electric current, or any way acted upon in its cojtrse, or in some part of its length ; as, in that case, it may transmit motion towards the periphery, and sensation towards the brain, simultaneously, — its two portions being polarized in directions contrary to each other. It has always been sought for as most important to be known, how the nerves terminate in the muscles, as well as in the other tissues they ramify. Dr. Waller has recently succeeded in following the course of the nerves to their ultimate ramifications with the greatest precision. He concludes that they arc seen to penetrate even into the interior of the muscular fibres, with which they intersect by loops in such a way that each ele- mentary fibril of nerve abuts upon an elementary muscle fibre. If this, beyond disputation, is uniformly so, it is no way wonderful that, where J the nerve is polarized by any cause, it should bring about the siniul- Fig. 51. A view of Straight Muscle Fibres, . showing how the Nerves called Motor taneous polarization of the fibre Fibrils terminate in and supply them, all «,u:„l^ :+ „u,.±~ if jl ' j. ± being very highly magnified Which it abuts. If tile lierve IS tet- anized, the muscle fibre is tetanized also. If there is sensation, the normal state is disturbed, which polarizes the nerve, and acts upon the brain. It is but reason that every cause which alters the capability of the molecular