.#--I have shown
the three phases of transformation, the intensity of one of the
constituent responses being varied by altering the intensity of
disturbance.

In the following record (fig. 68) I succeeded in obtaining a continuous
transformation from positive to negative phase by a continuous change in
the relative sensitiveness of the two contacts.

I found that traces of after-effect due to the application of
Na_2CO_3 remain for a time. If the reagent is previously applied to
an area and the traces of the carbonate then washed off, the increased
sensitiveness conferred disappears gradually. Again, if we apply
Na_2CO_3 solution to a fresh point, the sensitiveness gradually
increases. There is another further interesting point to be noticed: the
beginning of response is earlier when the application of Na_2CO_3 is
fresh.

[Illustration: FIG. 68.--CONTINUOUS TRANSFORMATION FROM NEGATIVE TO
POSITIVE THROUGH INTERMEDIATE DIPHASIC RESPONSE
Thick dots represent the times of application of successive stimuli.]

We have thus a wire held at one end, and successive uniform vibrations
at intervals of one minute imparted to the wire as a whole, by means of
a vibration head on the other end.

Owing to the after-effect of previous application of Na_2CO_3 the
sensitiveness of B is at the beginning great, hence the three resultant
responses at the beginning are negative or downward.

Dilute solution of Na_2CO_3 is next applied to A. The response of A
(up) begins earlier and continues to grow stronger and stronger. Hence,
after this application, the response shows a preliminary positive twitch
of A followed by negative deflection of B. The positive grows
continuously. At the fifth response the two phases, positive and
negative, become equal, after that the positive becomes very prominent,
the negative being reduced as a feeble after-vibration.

It need only be added here that the diphasic variations as exhibited by
metals are in every way counterparts of similar phenomena observed in
animal tissues.

CHAPTER XIV

INORGANIC RESPONSE--FATIGUE, STAIRCASE, AND MODIFIED RESPONSE

Fatigue in metals--Fatigue under continuous stimulation--Staircase
effect--Reversed responses due to molecular modification in nerve
and metal, and their transformation into normal after continuous
stimulation--Increased response after continuous stimulation.

[Illustration: FIG. 69.--FATIGUE IN MUSCLE (WALLER)]

[Illustration