446 ELECTRO-PHYSIOLOGY 



can be no doubt (in view of the conditions and behaviour of 

 the break excitation in muscle) that positive anodic polarisa- 

 tion is an expression of the same, i.e. the positive polarisation 

 current produced ly alterations of anodic points of the contractile 

 substance is an action current due to the break excitation from 

 the anode; an action current which behaves very differently 

 from the action current produced by the make excitation that 

 has so far exclusively concerned us. y 



The long persistence of negativity in the anodic points is 

 most remarkable ; it is easily explained by the fact that the 

 opening of a constant current under some conditions leads to 

 protracted excitation (persistent opening contraction) of the 

 muscle. This gradually declines, being more and more confined 

 to the anodic points of the muscle. But even when, as on sending 

 in weaker currents, or with a shorter duration of strong currents, 

 there is no visible persistent break contraction, or even break 

 twitch, there is nothing to prevent us from regarding the positive 

 polarisation current in question as the expression of opening 

 excitation lasting for a considerable period, since a low degree of 

 contraction is difficult or impossible of demonstration, especially 

 when it is confined to the immediate vicinity of the anodic or 

 kathodic points of the muscle, and since, moreover, negativity may 

 be present as the expression of excitation, without any trace of 

 contraction. 



Hermann's view of the positive anodic after -current only 

 differs from that of Hering inasmuch as, starting with the 

 assumption of an intrapolar electrotonus, he derives the action 

 current at break from the whole anelectrotonic tract of the 

 muscle. We have already seen, on the contrary, that if the 

 currents employed are not too strong, all the changes which can 

 collectively be termed " electrotonus " are strictly confined to the 

 physiological electrode points. 



Kathodic polarisation is almost exclusively negative in striated 

 muscle. It first appears on leading off in the sartorius, through 

 which current is passing, from the kathodic end and centre of the 

 muscle, with very weak currents, after a closure of several 

 seconds, increasing steadily with increase of current and longer 

 closure. If it is compared with the positive anodic after-current 

 which appears at the same end of the muscle, with equal 

 strength, and duration of closure, the latter soon becomes by far 



