OBSERVATION BY RHEOTOME ON ELECTRIC RESPONSE 47 



is 'set,' is kept pulled up by an electro-magnetic arrangement 

 shown in fig. 37, where the electro-magnet is seen to hold 

 a soft iron armature at the 

 end of the thread. At the 

 moment when stimulation is 

 to be effected the current 

 which energises the electro- 

 magnet is interrupted by an 



automatic arrangement which 

 will be described later. By 



FIG. 36. Arrangement for In- 

 stantaneous Stimulation 

 the break of the Current the Torsion-head set by string against stop Q 

 armature is released and a is suddenly let go by electro-magnetic 



release seen in fig. 37. 

 semi-vibration of the torsion- 

 head is suddenly produced, the amplitude of which has been 

 predetermined by suitable adjustment of the stop P. Suc- 



FIG. 37. General arrangement for Rheotomic Observation 



A, B, striking rods attached to revolving rheotomic disc ; K,, key for 

 electro-magnetic release of torsional stimulator ; K 2 , for unshunting the 

 galvanometer, G ; E, electro-magnet with its armature by which the 

 vibration-head, v, is set at a definite torsion-angle ; N,, N. 2 , non- 

 polarisable electrodes making electric contacts with specimen ;*c, com- 

 pensator. 



cessive stimuli of equal intensity may thus be applied on 

 the experimental tissue at whatever time may be desired. 



