STIMULATION OF MUSCLE AND NERVE 107 



It will be found that the cathodal half of 

 the muscle contracts first on closing, the anodal 

 half on opening the circuit. Evidently the 

 excitation began on closure at the cathode and 

 passed thence to the anode, while on opening 

 the circuit the excitation began at the anode 

 and passed to the cathode. 



In order to measure this interval accurately 

 the drum should be turned back until the writ- 

 ing point of the signal lies precisely in the ordi- 

 nate drawn by it during the experiment. The 

 muscle should then be stimulated. The ordinate 

 now drawn by the muscle with the drum thus 

 at rest will be synchronous with that drawn by 

 the signal during the experiment, and will mark 

 upon the abscissa of the muscle curve the moment 

 of stimulation, 



6. Tonic Contraction. Connect a dry cell 

 through an open simple key with the metre 

 posts of the rheochord. Connect non-polarizable 

 electrodes with the positive post and the slider. 

 Fasten one end of the curarized sartorius (pre- 

 pared with fragments of pelvis and tibia attached) 

 in the muscle clamp. Tie a thread to the other 

 end and fasten the thread to the upright pin of 

 the muscle lever. Let rion-polarizable electrodes 

 rest on the muscle near the respective ends. 

 tfse a strength of current that will just cause 



