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PHYSIOLOGY OF MUSCLE AND NERVE 



ful electromagnet possessing the shape of a horseshoe. A delicate thread of 

 silvered quartz or platinum is suspended in a vertical direction between its two 



FIG. 54. D'ARSONVAL GALVANOMETER AS MODIFIED BY ROWLAND WITH TELESCOPE 

 FOB OBSERVING MOVEMENTS OF NEEDLE. (Howett.) 



FIG. 55. SCHEMA OF GALVANOMETER. 



n, a, North and south poles of astatic pair of magnets ; m, compensating magnet, held 

 by friction on the staff, and capable of being approached to, or rotated with reference to, 

 the suspended magnet; X , mirror; /, fiber supporting the magnets; c, c, c, c, coils of wire 

 to carry the electric current near to the magnets, the upper coils being wound in the 

 opposite'direction to the lower; e, e, non-polarizable electrodes applied to the longitudinal 

 surface and cross-section of a muscle. (American Text-book of Physiology.) 



poles. The sides of these poles are perforated so that the shadow of this string may 

 be reflected upon a screen or upon the sensitive paper of a photographic camera. 



