iv ELECTROMOTIVE ACTION IN MUSCLE 441 



deflections in one direction only derives from the remarkable 

 variations in magnitude exhibited under approximately equal 

 conditions. This affords a prima facie explanation of the striking 

 fact that the galvanic effects of excitation are often insignificant, 

 even in preparations made from fresh, vigorous animals, and ma^ 

 fail altogether at a certain medium strength of current. This 

 must indeed follow inevitably, where the two antagonistic processes 

 terminate simultaneously as regards the electrical changes which 

 they effect in the muscle. Finally, both the diphasic action and 

 the interference phenomena before alluded to (positive after varia- 

 tion and oscillation of the magnet to a new equilibrium) conform 

 with the above theory. If we are to explain the monophasic, but 

 antagonistic effects, of minimal and maximal excitation, we must 

 assume in the first case a more prompt reaction of the in- 

 hibitory (assimilatory) processes, in the other a preponderance 

 of the process initiated in the muscle by the exciting (dissimi- 

 latory) fibres. 



Moreover, we find experimentally that no artificial excitation 

 of the nerve produces that state of fatigue in the muscle in which 

 it is characterised by a special disposition to positive galvanic 

 effects, while these never fail to appear when fatigue is induced 

 by natural excitation of the nerve from the central organ. This 

 difference is intelligible on the assumption that in the last case 

 the exciting fibres are alone, or mainly, involved, while in arti- 

 ficial excitation both kinds of fibres are necessarily excited 

 simultaneously, so that the resulting changes of the muscle in 

 either case must be dissimilar. 



And lastly, we must emphasise the fact that in indirect 

 excitation of the adductor muscle the galvanic effects are by no 

 means in such close relation with the mechanical effects of 

 excitation as might be concluded from countless experiments on 

 vertebrate nerve -muscle preparations. Kather, as has been 

 shown, there is a fundamental independence of the two, since not- 

 withstanding the marked contraction of the muscle, the galvanic 

 effects of excitation are but slightly developed under some con- 

 ditions although in the right direction (negative variation) 

 while at other times they fail altogether, or appear as a positive 

 variation. From this we must conclude, in view of the preced- 

 ing observations, that the antagonistic relation of the two processes 

 simultaneously excited in the muscle may bear a different value 



