by animal nerve in condition of extreme sub-tonicity. This abnormal response of the nerve is also transformed into normal under continuous stimulation.
Returning to the response of metals we may distinguish the following typical cases. Beginning with the case of extreme molecular modification, we have (1) a condition which gives rise to the abnormal or negative response; after continued vibration the negative becomes less negative, and ultimately becomes converted into positive: (2) an irresponsive or neutral condition; vibration or annealing transforms it into positive: (3) a sluggish, feebly positive, becoming more and more positive after continued vibration: (4) a steady and permanent condition, when the responses are uniform: and lastly (5) when vibration is maintained for too long a time, the positive tends to become less positive, the responses decline—a state of things which is designated as fatigue.
Increased Electromotive Response under increased Intensity of Stimulus
When the intensity of stimulus is increased by increasing the amplitude of vibration, the electric res-
Fig. 79. Photographic records of responses (a) from 5° to 40°, (b) from 40° back to 5°. The vertical line = 0.1 volt.
