THE PRODUCTION OF ENERGY IN MUSCLE 107 



ately thereafter a deflection in the opposite direction, to prove that 

 the distant pole of the muscle has now become active and negative. 



While the ordinary type of galvanometer is sufficiently sensitive 

 to perceive these electrical variations, its action is altogether too slow 

 to follow them with accuracy. Although less sensitive, the strong gal- 

 vanometer is more serviceable for these tests, because it possesses a 

 much greater motility. There is one way, however, in which even the 

 ordinary galvanometer may be made to indicate the current of action 

 and that is, to cause its needle to be deflected first of all by the current 

 of injury. Thus, if one of the non-polarizable electrodes is placed 

 against the cross-section of the muscle, while the other is applied to its 

 equatorial surface, the galvanometric needle will be forced to assume a 

 fixed lateral position. If the distant non-injured portion of this muscle 

 is now stimulated, the subsequent contraction of this region must give 

 rise to a negativity which travels from here toward the other end of 

 the muscle. As this contraction-wave and its negativity passes the 

 plus lead of the current of injury, it reduces this positivity and causes 

 the needle to swing toward and beyond zero. Inasmuch as the needle 

 is deflected at this time in a direction opposite to that forced upon it by 

 the initial current of injury, this phenomenon has frequently been 

 designated as a " negative variation" of the primary demarcation 

 current. This arrangement, therefore, permits the negativity ac- 

 companying the wave of contraction of muscle, to neutralize the posi- 

 tivity of the current of injury in the equatorial region of the muscle. 

 Whether it will do that fully, depends upon the temperature and elas- 

 tic tension of the muscle, but we might say that under favorable con- 

 ditions the current of injury may equal 0.04 volt, while the current of 

 action may amount to as much as 0.08 volt. 1 Clearly, the distance to 

 which the needle will be deflected by the action current depends 

 upon the strength of the latter, i.e., upon the measure in which it is 

 able to neutralize the initial current of injury. 



The relationship existing between the wave of contraction and the 

 current of action has been studied by photographing the variations of 

 the galvanometric indicator together with the movements of two levers 

 placed horizontally upon the surface of the muscle near the non-polar- 

 izable electrodes. It may be inferred that these two factors are very 

 closely allied to one another, but the records obtained by the method 

 just mentioned, indicate that the electrical changes antecede the move- 

 ments of the corresponding lever by a fraction of a second. Two 

 views may therefore be formulated, namely, (a) the electrical changes 

 constitute the wave of excitation in consequence of which certain chem- 

 ical alterations are instigated which eventually give rise to the shorten- 

 ing of the muscle, or (6) the electrical differences are the result of the 

 chemical changes set off by the wave of excitation and are the fore- 

 runner of the mechanical effects. It is quite impossible at this time to 

 decide this question one way or another. 



1 Piper, Pfluger's Archiv, cxxix, 1909, 145, and Jensen, ibid., Ixxvii, 1899, 137. 



