100 



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 



iitii " ' 4 



Fig. 64. — D'Absonval Galvanometer as Modified by Rowland With Telescope 

 FOB Obseeving Movements of Needle. (Howell.) 



Fig. 55. — Schema of Galvanometer. 



n, s. 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. 



