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PHYSIOLOGY 



the impulse, which normally travels down the motor nerve from the anterior 

 cornual cell to the muscle, is discontinuous, and therefore that on leading 

 off a motor nerve to a galvanometer we ought to obtain electrical oscillations 

 of fifty distinct stimuli per second. Dittler has investigated by means of 

 the string galvanometer the electrical changes accompanying the ordinary 

 contractions of the diaphragm, and also those occurring in the phrenic 



FIG. 93. 



Electrical variations produced by voluntary contractions of 

 human muscle. (PiPER.) 



nerve. He finds that both in the muscle and in the nerve there is evidence 

 that each contraction is a fused series of single contractions, evoked by 

 the discharge along the nerve of between fifty and seventy excitations per 

 second. So far therefore the evidence is in favour of the view that volun- 

 tary contraction and, one must add, the tonic contractions of all skeletal 

 muscles, are discontinuous in nature and analogous to the tetanus which 

 we may evoke artificially by rapid stimulation either of muscle or of its 

 motor nerve. 



