CURRENT OF INJURY AND NEGATIVE VARIATION 151 



place, when a portion of it was subjected to any molecular 

 disturbance, an electro-motive difference was induced, as 

 between the molecularly disturbed or excited and the un- 

 disturbed areas. The intensity of this electro-motive change, 

 in the second place, was seen to increase with intensity 

 of excitation. And, thirdly, the recovery from excitation 

 was seen to be delayed, where the intensity of stimulus 

 was strong (fig. 105). This is shown in the electrical 



FIG. 105. Photographic Record showing Persistent Electrical After-Effect 

 in Inorganic Substance under Strong Stimulation. Note the tilt of 

 base-line upwards 



The vertical line to the right represents - i volt. 



response of tin as a persistent after-effect, the sign of 

 which is the same as that of the excitatory electro-motive 

 change. 



A similar state of things is exhibited mechanically in a 

 torsioned wire. When the torsion is moderate, and the 

 molecular distortion slight, the released wire quickly re- 

 covers its original position of equilibrium. But when the 

 torsion is excessive and the wire strained beyond a certain 

 limit, it remains for a long time in a torsioned condition, 



