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MUSCLE-NERVE PHYSIOLOGY 



lines into which it was supposed the fibers are thrown in contraction is due 

 to the relaxation of a fiber which has been recently contracted and is not 

 at once stretched again by some antagonist fiber or whose extremities are 



FIG. 322. Reflecting Galvanometer. (Thomson.) A, The galvanometer, which 

 consists of two systems of small astatic needles suspended by a fine hair from a support, so 

 that each set of needles is within a coil of fine insulated copper wire; that forming the lower 

 coil is wound in an opposite direction to the upper. Attached to the upper set of needles 

 is a small mirror about ^ inch in diameter; the light from the lamp at B is thrown upon this 

 little mirror, and is reflected upon the scale on the other side of B, not shown in figure. 

 The coils u are arranged upon brass uprights, and their ends are carried to the binding- 

 screws. The whole apparatus is placed upon a vulcanite plate capable of being leveled 

 by the screw supports, and is covered by a brass-bound glass shade, /, the cover of which 

 is also of brass, and supports a brass rod, &, on which moves a weak curved magnet, m. 

 C is the shunt by means of which the amount of current sent into the galvanometer may 

 be regulated. When in use, the scale is placed about three feet from the galvanometer, 

 which is arranged east and west, the lamp is lighted, the mirror is made to swing, and the 

 light from the lamp is adjusted to fall upon it, and it is then regulated until the reflected 

 spot of light from it falls upon the zero of the scale. The wires from the non-polarizable 

 electrodes touching the muscle are attached to the outer binding-screws of the galvan- 

 ometer, a key intervening for short-circuiting; or if a portion only of the current is to pass into 

 the galvanometer the shunt should intervene as well with the appropriate plug in. When 

 a current passes into the galvanometer the needles and, with them, the mirror are turned 

 to the right or left according to the direction of the current. The amount of the deflection 

 of the needle is marked on the scale by the spot of light traveling along it. 



kept close together by the contractions of other fibers. The contraction is 

 therefore a simple and, according to Edward Weber, a uniform, simultaneous, 

 and steady shortening of each fiber and its contents. What each fibril or 



