IV 



ELECTROMOTIVE ACTION IN MUSCLE 



337 



current is stronger in proportion as the animal is higher in the 

 scale, but it is difficult to get exact measurements of E.M.F. 

 in warm-blooded muscles, on account of the rapid death of the 

 tissue. That the muscle current is essential to the preservation 

 of normal vital activities in the muscle appears directly from the 

 fact that dead muscle has no electromotive action, or at most 

 exhibits excessively irregular and weak reactions. Moreover, the 

 E.M.F. of the excised muscle, 

 provided with a cross-section, 

 undergoes, as du Bois pointed 

 out, a slow decline ; the pro- 

 cess of death, creeping slowly 

 from the cut surface, gradually 

 involves all the injured fibres 

 of a muscle, so that they be- 

 come rigored and incapable of 

 electromotive action. Accord- 

 ingly, the limit between dead 

 fibres (confined at first to the 

 cut surface) and the living part 

 of the contractile substance 

 (" the demarcation surface ") 

 encroaches inwards in the 

 course of the rigor. 



We have frequently used 

 the term " artificial section," 

 even when there was no real 

 cut surface, but only a de- 

 marcation surface as above. 

 As a matter of fact each 



Fto. 1076. 



dead bit of muscle -fibre be- 

 haves as an indifferent tag (comparable with the tendon 

 substance), which leads off from the artificial cross - section, 

 i.i'. limit between dead and living fibres. In this sense, 

 therefore, it is quite legitimate to speak of a mechanical, 

 thermic, or chemical section. As a general rule, moreover, the 

 strength of the electromotive action is independent of the kind of 

 death, or destruction, of a tract of fibres, so long as the process 

 is actually accomplished. 



If these experiments prove beyond doubt that the muscle 



z 



