ELECTROTACTILE DETECTION OF EXCITATORY PULSE 259 



by the use of the electrothermic stimulator. In any case, it 

 is easy to discriminate between the effect of any such ex- 

 traneous disturbance and the true excitatory effect in transit 

 for which we are looking ; for the effect of the former, if it 



Fig. 106. 



Electrotactile Method for Detection of Excitatory Wave 

 during Transit 



Stem placed under light pressure between B and sliding rod c. A, B, elec- 

 tric contact points, the pressure of which is delicately adjusted by 

 micrometer screw, M. A moderate current flows round the circuit, 

 including the contact points, A B, and the galvanometer, G, the 

 E.M.F. being suitably adjusted by the potentiometer slide, P Stimu- 

 lation of stem effected by momentary closure of key, k, in circuit 

 with electrothermic stimulator. Excitatory wave reaching the zone B, c, 

 causes pressure-variation, with concomitant galvanometric response. 



occurs, is immediate, whereas that due to excitation takes 

 place after a definite interval from the application of stimulus. 

 In the experiment of which the record is given in fig. 107, 

 stimulus was applied at a distance of 4 cm. The excitatory 

 wave reached the experimental zone after an interval of five 



