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MUSCLE-NERVE PHYSIOLOGY 



This has been proved for entire muscles, by making a mass of muscles, or many 

 fibers together, contract in a vessel full of water, with which a fine, perpen- 

 dicular, graduated tube communicates. Any diminution of the bulk of the 

 contracting muscle would be attended by a fall of fluid in the tube; but when 



m 



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 

 K 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, b, on which moves a weak 

 curved magnet, m. C is the shunt by means of which the amount of current sent into the galvanom- 

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

 which is a ranged 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 uncil 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 galvanometer, 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 cur- 

 rent. The amount of the deflection of the needle is marked on the scale by the spot of light traveling 

 along it. 



the experiment is carefully performed, the level of the water in the tube re- 

 mains the same, whether the muscle be contracted or not. 



In thus shortening, muscles appear to swell up, becoming rounder, more 

 prominent, harder, and apparently tougher. But this hardness of muscle in 

 the state of contraction is not due to increased firmness or condensation of the 



