THE PRODUCTION OF ENERGY IN MUSCLE 



105 



In explanation of this phenomenon, it should be stated first of all 

 that the active portion of a muscle possesses a different electrical po- 

 tential from the resting portion. Thus, if a perfectly normal muscle is 

 brought into the circuit of a galvanometer by means of non-polarizable 

 electrodes, the excitation of one of its ends immediately produces a de- 

 flection of the needle (Fig. 60) . If the direction of this deviation is now 

 noted, it will be seen that the current flows through the galvanometric 

 circuit from the unexcited to the excited portion of the muscle. Its 

 resting part, therefore, is electropositive to its contracting part. In- 

 side the muscle, of course, the current flows from the contracting to 

 the resting portion, the former being positive and the latter nega- 

 tive. But, as has been stated above, we usually designate the direc- 

 tion of these currents in accordance with their flow through the 

 galvanometer. 



Fig. 59, — The Rheoscopic Frog 

 Preparation. 

 Muscle A stimulated through its nerve 

 at S, generates an action current which 

 causes muscle B to contract. 



Fig. 60. — Current of Action. 



M, muscle; G, galvanometer; S, seat^ 



of stimulation. 



In accordance with these results, it must now be evident that the 

 preceding experiment with the rheoscopic frog preparation, actually 

 proves the occurrence of an electrical variation in muscle in conse- 

 quence of its activity. Muscle B serves in this case the purpose of a 

 galvanometer, because its contraction indicates that such a current is 

 actually present. It may be concluded, therefore, that the excita- 

 tion of nerve A gives rise to a contraction of muscle A, in the course of 

 which an action current is set up in its substance which serves as a 

 stimulus for nerve B. The impulse generated in the latter produces 

 a contraction of muscle B. The function of muscle A with regard to 

 muscle B may therefore be likened to that of a battery. In order to 

 avoid the possible criticism that the activation of muscle B is caused 

 by an escape of the current used to stimulate, it is advisable to subject 

 nerve A to mechanical impacts, or to modify the entire experiment by 

 placing nerve B lengthwise upon the beating heart of a mammal.^ 

 1 Kollicker, Miiller's Archiv, vi, 1856, 528. 



