334 PROTOPLASMIC ACTION AND NERVOUS ACTION 



The normal tetanic contractions of voluntary muscles 

 are thus summated contractions resulting from rhythmi- 

 cal innervation. We can thus understand why the 

 summated contraction resulting from artificial rhythmical 

 electrical stimulation of the muscle is physiologically 

 indistinguishable from the normal contraction; in 

 reality the natural as well as the artificial tetanus is a 

 result of rhythmical electrical stimulation. Whether 

 the initial electric disturbance in the muscle cell originates 



Temperature Number of Waves 



f 15 



12 19-20 



155 25 



18 29 



20 32-33 



22 35 



24 38 



26 40-41 



28 44 



30 47 



3^ 51 



34 54 



36 56 



at the motor end-plate or at the point of entrance of a 

 current from an external stimulating electrode is a matter 

 of indifference, so far as the response of the living tissue 

 is concerned. In the intact organism under normal 

 conditions the rate of rhythm is fixed or predetermined 

 by the constitution of the motor cells in the nervous 

 system. These cells, however, are subject to influence 

 by external conditions, such as temperature or the 

 composition of the surrounding medium (e.g., H-ion 

 concentration), so that many physiological rhythms are 



