STIMULATION OF MUSCLE AND NERVE 145 



oscillations are produced by the difference of 

 potential created by each contraction wave as it 

 passes over the muscle (contracting muscle is 

 negative towards muscle at rest, see page 302), 

 arid demonstrate that the tetanus is a fusion 

 of individual contractions produced by successive 

 stimuli. 



Hence, nerve, like muscle, responds to a contin- 

 uous stimulus by a periodic discharge of energy. 



Ulnar Nerve. Connect 15 dry cells in series 

 (zinc to carbon), and join the last zinc and carbon 

 through a key to a small brass stimulating 

 electrode one cm. in diameter, and a large " in- 

 different" electrode (brass plate 6.5 x 3.5 cm. 

 covered with cotton wet in solution of common 

 salt). Hold the indifferent electrode in the left 

 hand, and apply the stimulating electrode to the 

 ulnar nerve at the elbow. 



A peculiar tingling sensation will be felt so 

 long as the current flows. 



Polarization Current. Let the sciatic nerve 

 rest on a pair of non-polarizable electrodes in 

 the moist chamber. Connect the electrodes to 

 the side cups of the pole-changer (without cross- 

 wires). Connect one end pair of the pole-changer 

 cups with a dry cell. Turn the rocker to the 

 opposite side to prevent the battery current from 

 reaching the electrodes until it is wanted. Con- 

 10 



