INORGANIC RESPONSE 119g 
many days (fig. 71). While discussing the subject of 
fatigue in plants, I have adduced considerations which 
showed that the residual 
effect of strain was one 
of the main causes for 
the production of fatigue. 
This conclusion receives 
independent support from 
the records obtained with 
metals. 
In this connection the 

important fact is that the 
various typical fatigue Fic. 71.—FaticurE sHowN By TIN 
- ac : ae WIRE WHICH HAD BEEN CONTINU- 
effects exhibited in living OUSLY STIMULATED FOR SEVERAL 
substances are exactly re- a 
produced in metals, where there can be question neither 
of fatigue-product producing fatigue effects, nor of those 
constructive processes by which they might be removed. 
We have seen, both in muscles and in plants, that if 
sufficient time for complete recovery be allowed between 
each pair of stimuli, the heights of successive responses 
are the same, and there is no apparent fatigue (see 
page 39). But the height of response diminishes as 
the excitation mterval is shortened. We find the same 
thing in metals. Below is given a record taken with 
tin (fig. 72). Throughout the experiment the amplitude 
of vibration was maintained constant, but m (a) the 
interval between consecutive stimuli was 1’, while in (0) 
this was reduced to 30”. A diminution of height 
immediately occurs. On restore the original rhythm 
as in (¢), the responses revert to their first large value. 
