PHYSIOLOGY OF MCSCI.KS ANU NERVES. 



traction nf tliis sort i< called (,f<ntnx of the muscle to 

 distimnii-h it from ;i serie- of di-t iu.-t pul-at ion-. 



Another method of frequently and n-peatedlv do- 

 sing and opening the current is by means of a self- 

 acting apparatus which is put in motion by the current 

 itself. This, \\hich is called Warner's hanuner, is re- 

 presented in ti^ - . 1^. The current of the chain i- con- 

 ducted through the column 

 represented on the ri^ht to 

 the ( ierman silver spring <;. 

 A small platinum plate c is 

 soldered on to the latter, and 

 is pressed against the point 

 above it by the elastic force 

 of the spring. The cun'ent 

 passes from this to the coil-; 

 of a small electro-magnet, 

 and, after pas-in^ through 

 this, back to the chain 



through the clamp connected with it on I he left. An 

 armature of soft iron, /,, fastened on to the <prin^ 

 O o, i- >u-pended over the poles of the electro-magnet. 

 This iron beiu^ at t ract ed by the electro-magnet, the 

 >mall plate < is forced away from the point and the cur- 

 rent i< thus interrupted. In so doin^. h:>\\e\er, the 

 electro-magnel parts with its magnetism, and conse- 

 quently relinquishes it- hold upon the armature; the 

 plate is thus arain prosed by the action ,,f the 

 sj)riiiL( against the point. The current being thus again 

 c!o>ed, the electro-magnet reco\crs its force, a ^a i ii at- 

 tract- the armat lire, and a^ain interrupts the current ; 

 and these processes are e.intinued as I 'in^ as the chain 

 remain-- inserted between tin- column on the rififhi and 



FIG. 12. WAGSKK'S HAM.MKU. 



