104 RESPONSE IN THE LIVING AND NON-LIVING 
CHAPTER XIII 
INORGANIC RESPONSE—MOLECULAR MOBILITY : 
ITS INFLUENCE ON RESPONSE 
Effects of molecular inertia—Prolongation of period of recovery by over- 
strain—Molecular model—Reduction of molecular sluggishness attended 
by quickened recovery and heightened response—Effect of temperature 
—Modification of latent period and period of recovery by the action of 
chemical reagents—Diphasic variation. 
WE have seen that the stimulation of matter causes 
an electric variation, and that the acted substance 
eradually recovers from the effect of stimulus. We 
shall next study how the form of response-curves is 
modified by various agencies. 
In order to study these effects we must use, in 
practice, a highly sensitive galvanometer as the recorder 
of E.M. variations. This necessitates the use of an 
instrument with a comparatively long period of swing 
of needle, or of suspended coil (as in a D’Arsonval). 
Owing to inertia of the recording galvanometer, however, 
there is a lag produced in the records of H.M. changes. 
But this can be distinguished from the effect of the mole- 
cular inertia of the substance itself by comparing two 
successive records taken with the same instrument, in 
one of which the latter effect is relatively absent, and 
inthe other present. We wish, for example, to find out 
