iv ELECTROMOTIVE ACTION IN MUSCLE 455 



with negative fore-swing). There can be no doubt that the positive 

 kathodic after -current is in this case produced Toy an inhibition 

 (developed at the physiological kathode at break of the exciting 

 current) of the existing persistent excitation, and consequent relative 

 positivity of the points of fibres in question. 



As we have repeatedly had occasion to observe, the effects of 

 the changes in the excited muscle-substance produced under the 

 influence of the anode, during closure of the current, are analogous 

 in every particular to those which are perceived under the same 

 conditions at the kathode on opening the current. This is true, 

 not merely in regard to change of form in the muscle (which in 

 both cases may be identified as a localised relaxation), but also of 

 the concomitant electromotive phenomena, characterised by relative 

 positivity of the entrance, or exit, points of the current, by which 

 a negative anodic, or positive kathodic, after-current is produced 

 respectively. Since the method of investigating secondary 

 electromotive phenomena only determines the consequences of 

 electrical excitation after .opening the polarising current, it is 

 evident that given the conditions necessary to the discharge 

 of a visible break excitation, e.g. application of stronger currents 

 and longer duration of closure the positive anodic after-current 

 which this produces will become prominent, while the negative 

 after-current only appears occasionally as a fore-swing. Only in 

 the case in which the appearance of the break excitation is 

 in any way hindered or prevented can we expect to see marked 

 effects in the direction of a negative anodic after-current, as, e.g., in 

 exhausted preparations, or after killing the anodic ends of fibres. 



It is not therefore surprising that muscles which are 

 ab initio in a state of persistent excitation (tonic contraction) 

 should react to current, both as regards visible changes of form 

 and galvanic after-effects, analogously with veratrinised muscle. 

 It is clear that the phenomena of inhibition, which appear 

 during closure at the anode, on opening at the kathode, in 

 contracted cardiac, as well as in holothurian, muscle, must corre- 

 spond with positivity of the points in question as against all 

 others ; in the adductor muscle of anodonta also (which is 

 characterised by pronounced tonus), not only negative anodic, but 

 also positive kathodic polarisation must from experimental data 

 be reckoned among the regular consequences of the passage of the 

 electrical current (71). 



