114 RESPONSE IN THE LIVING AND NON-LIVING 
much earlier than that of B. The resultant curve R’ 
was obtained by summation. 
After taking the records of A and B separately, a 
record of resultant effect R due to simultaneous vibra- 
tion of A and B was next taken. It gave the curious 
two-phased response — positive effect followed by 
negative after-vibration, practically similar to the re- 
sultant curve R’ (fig. 66, b). 
The positive portion of the curve is due to A effect 
and the negative to B. If by any means, say by 
elther increasing the amplitude of vibration of A or 
increasing its sensitiveness, the response of A is very 
greatly enhanced, then the positive effect would be 
predominant and the negative effect would become 
inconspicuous. When the two constituent responses 
are of the same order of magnitude, we shall have a 
positive response followed by a negative after-vibration ; 
the first twitch will belong to the one which responds 
earlier. If the response of A is very much reduced; 
then the positive effect will be reduced to a mere 
twitch and the negative effect will become predominant. 
I give aseries of records, fig. 67, in which these three 
principal types are well exhibited, the two contacts 
having been rendered unequally excitable by solutions 
of the two reagents KBr and Na,CO;.. A and B were 
vibrated simultaneously and records taken. (a) First, 
the relative response of B (downward) is increased by 
increasing its amplitude of vibration. The amplitude 
of vibration of A was throughout maintained constant. 
The negative or downward response is now very con- 
spicuous, there being only a mere preliminary indication 
