138 RESPONSE IN THE LIVING AND NON-LIVING 
of observations for an entire cycle, that is to say, a 
series of observations were taken for maximum effects, 
starting from amplitude of vibration of ‘10° and ending 
in 100°, and backwards from 100° to 10°. Effect of 
hysteresis 1s very clearly seen (see A, fig. 87); there 
is a considerable divergence between the forward and 
return curves, the return curve being higher. On re- 
peating the cycle several times, the divergence is found 
very much reduced, the wire on the whole is found to 
assume amore constant sensitiveness. In this steady 
condition, generally speaking, the sensitiveness for 
smaller amplitude of vibration is found to be greater 
than at the very beginning, but the reverse is the case 
for stronger intensity of stimulation. 
Effect of annealing.— I repeated the experiment with 
the same wire, after pourme hot water into the cell and 
allowing it to cool to the old temperature. From the 
cyclic curve (B, fig. 87) it will be seen (1) that the sen- 
sitiveness has become very much enhanced; (2) that 
there is relatively less divergence between the forward 
and return curves. Even this divergence practically 
disappeared at the third cycle, when the forward and 
backward curves coincided (Cc, fig. 87). The above 
results show in what manner the excitability of the wire 
is enhanced by purely physical means. 
It is very curious to notice that addition of Na,CO, 
solution (see Chap. XV—Action of Stimulants) produces 
enhancement of responsive power similar to that pro- 
duced by annealing ; that is to say, not only is there a 
ereat increase of sensitiveness, but there is also a 
reduction of hysteresis. 
