AFTER-EFFECT OF STIMULUS ON CONDUCTIVITY 505 



lated point in the middle, were exactly equal and balanced. 

 The fact that after this application, however, there are 

 resultant responses which are upwards, shows, as already 

 said, that by the moderate stimulation of the right-hand 

 side, both excitability and conductivity have been increased. 

 The resultant upward response here is, then, in the same direc- 

 tion as the so-called ' current of injury,' and forms, as it were, 

 a positive variation of it. 



In another experiment, in which I wished to try the 

 effect of excessive stimulation, instead of applying a hot 

 solution at 60 C., I produced 

 greater injury and consequent 

 excessive stimulation, by scorch- 

 ing the nerve at the same point 

 as before, with a red-hot platinum 

 wire. In this case resultant 

 response was downwards, show- 

 ing that the excitability and 

 conductivity of the right-hand 

 side of the balance had been 

 depressed by over-stimulation. 



I was next desirous of 

 demonstrating that the excita- 

 bility of the over-stimulated or 

 excited point undergoes depres- 

 sion. For this purpose I took 

 a fresh specimen and first ob- 

 tained a state of balance. Similar excitation of E' and E 

 produced a balanced or null effect. The point E was then 

 injured by touching it with a hot platinum wire. On now 

 proceeding to take records, it is seen that the responses 

 were downwards, showing the depression of excitability at 

 the injured E (fig. 312). 



The fact that galvanometric negativity had been induced 

 at E, by reason of injury, is demonstrated at the beginning 

 of the record as an up-line. The subsequent resultant 

 responses due to simultaneous excitation of E and E' are 



FIG. 312. Photographic Record 

 showing Effect of Excessive 

 Stimulation in Depressing Ex- 

 citability and Conductivity 



Up-line at starting shows the rest- 

 ing-current due to after-effect of 

 stimulation. The upsetting of 

 balance in a downward direction 

 constitutes a negative variation 

 of the resting-current, and shows 

 depression of conductivity and 

 excitability. 



