306 



THE SO-CALLED SECONDAEY ELECTROMOTIVE 



ance is the strength of the first 4- anodal after-current relatively to 

 the second effect, the former with weak currents frequently ap- 

 pearing- alone ; further the second phase is not, as in the case of 

 nerve, stronger than the kathodal after-current, but on the contrary 

 is always markedly weaker ; it is, however, always of longer dura- 

 tion. The law for muscle may therefore be expressed as follows : 

 on breaking a polarising current, there appears on each side an after' 

 current having the same direction as the previous polarising one (i. e. 

 -f ) ; this is followed on the side of the anode by an opposed de- 

 flection of long duration, whereas on the side of the kathode the + 

 after-current shows no such opposite phase, but attains a very marked 

 strength and then completely disappears. In a few instances (of which 

 the second example is one) I saw with weak currents, a double 

 effect, first 4- then on the side of the kathode. The follow- 

 ing are examples of the facts described. 



Example of an experiment on nerves. Two sciatic nerves placed 

 side by side in alternating directions (as in previous experiments). 

 Extrapolar leading off at CC'. Duration of closure short as possible. 



B' 



Long polarised region AB. 



Short polarised region AB'. 



