442 ELECTRO-PHYSIOLOGY CHAP. 



with respect to the mechanical effects of excitation and to the electro- 

 motive reaction ; since here the consequences of excitation, and 

 there of the simultaneous inhibition, preponderate, or are alone 

 manifested. 



We must further point out the analogy between this reaction 

 of the adductor muscle and the observations of Fano on the 

 cardiac muscle of the tortoise, where, also, there is imperfect 

 correspondence between the changes of form in the muscle and 

 its simultaneous electrical manifestations (66). 



IV. SECONDARY ELECTROMOTIVE ACTION IN MUSCLE 



In muscle (as in nerve, electrical organs, and irritable proto- 

 plasm in general) the passage of the electrical current is followed 

 by certain electromotive reactions, which are intimately related 

 with the action current, and are to a certain extent only a special 

 form of its manifestation. As early as 1834, Peltier discovered 

 that frogs' limbs, or isolated muscles, or even pieces of muscle, 

 developed a current in the reversed direction. 



Du Bois-Eeymond (67), who took up the investigation later, 

 convinced himself that the secondary current (after-current) is 

 not exclusively, if at all, dependent on the polar zones, but is 

 also initiated in the tracts lying between them, since he found 

 that any given section of the intrapolar tract of a muscle 

 traversed longitudinally gave an electromotive response in the 

 same direction, on opening the polarising current ; accordingly 

 he advanced the view that this effect mainly depended on so- 

 called " internal polarisation." 



Many inorganic and organic porous bodies, saturated with an 

 electrolyser, do actually possess the property of acquiring negative 

 internal polarisation. The polarising current then divides itself 

 between the badly conducting, saturating fluid, and the porous 

 vessel, the latter being polarised from the zones. "Each of 

 the countless intermediate points now gives an electromotive 

 reaction in the reverse direction from that in which it was 

 traversed by the current." The superposition of all these partial 

 currents results in the branch current, which passes through the 

 deriving circuit. Each coextensive tract in any such regularly 

 constructed prismatic, or cylindrical, body gives, as a rule, a strong 

 secondary electromotive reaction after the passage of the current. 



