122 RESPONSE IN THE LIVING AND NON-LIVING 
is seen under particular conditions in the response of 
certain muscles (fig. 74, a). It is also observed some- 
times even in nerve, which otherwise, generally speaking, 
gives uniform responses. Of this effect, no satisfactory 
theory has as yet been offered. It is in direct contra- 
diction to that theory which supposes that each 
stimulus is followed by dissimilation or break-down of 
the tissue, reducing its function below par. For in these 
cases the supposed dissimilation is followed not by a 
decrease but by an increase of functional activity. This 
‘staircase. effect’ I have shown to be occasionally 
exhibited by plants. I have 
also found it in metals. In 
the last chapter we have 
seen that a wire often falls, 

especially after resting for 
(a) (db) 
a lone time, into a state of 
Fia. 74.—‘ STAIRCASE ’ EFFECT 5 < ? 
(a) in muscle (after Engelmann). comparative — sluggishness, 
(b) in metal. ; 
and that this molecular 
inertness then gradually gives place to increased 
mobility under stimulation. As a consequence, an 
increased response is thus obtained. I give in fig. 74, 6, 
a series of responses to uniform stimuli, exhibited by 
platinum which had been at rest for some time. This 
effect is very clearly shown here. So we see that im 
a substance which has previously been in a sluggish 
condition, stimulation confers increased mobility.  Re- 
sponse thus reaches a maximum, but continued stimu- 
lation may afterwards produce overstrain, and the 
subsequent responses may then show a decline. This 
consideration will explain certain types of responses 
