Response in the Living and Non-Living | Page 7

mechanical response is also
available, it is found that the electrical and mechanical records are
practically identical.
The two response-curves seen in the accompanying diagram (fig. 5),
and taken from the same muscle by the two methods simultaneously,
clearly exhibit this. Thus we see that electrical response can not only
take the place of the mechanical record, but has the further advantage
of being applicable in cases where the latter cannot be used.
#Electrical response: A measure of physiological activity.#--These
electrical changes are regarded as physiological, or characteristic of
living tissue, for any conditions which enhance physiological activity
also, pari passu, increase their intensity. Again, when the tissue is
killed by poison, electrical response disappears, the tissue passing into
an irresponsive condition. Anæsthetics, like chloroform, gradually
diminish, and finally altogether abolish, electrical response.
[Illustration: FIG. 5.--SIMULTANEOUS RECORD OF THE
MECHANICAL (M) AND (E) ELECTRICAL RESPONSES OF THE
MUSCLE OF FROG. (WALLER.)]
From these observed facts--that living tissue gives response while a
tissue that has been killed does not--it is concluded that the
phenomenon of response is peculiar to living organisms.[5] The
response phenomena that we have been studying are therefore
considered as due to some unknown, super-physical 'vital' force and are
thus relegated to a region beyond physical inquiry.
It may, however, be that this limitation is not justified, and surely, at
least until we have explored the whole range of physical action, it
cannot be asserted definitely that a particular class of phenomena is by
its very nature outside that category.
#Electric response in plants.#--But before we proceed to the inquiry as
to whether these responses are or are not due to some physical property
of matter, and are to be met with even in inorganic substances, it will
perhaps be advisable to see whether they are not paralleled by

phenomena in the transitional world of plants. We shall thus pass from
a study of response in highly complex animal tissues to those given
under simpler vital conditions.
Electric response has been found by Munck, Burdon-Sanderson, and
others to occur in sensitive plants. But it would be interesting to know
whether these responses were confined to plants which exhibit such
remarkable mechanical movements, and whether they could not also be
obtained from ordinary plants where visible movements are completely
absent. In this connection, Kunkel observed electrical changes in
association with the injury or flexion of stems of ordinary plants.[6] My
own attempt, however, was directed, not towards the obtaining of a
mere qualitative response, but rather to the determination of whether
throughout the whole range of response phenomena a parallelism
between animal and vegetable could be detected. That is to say, I
desired to know, with regard to plants, what was the relation between
intensity of stimulus and the corresponding response; what were the
effects of superposition of stimuli; whether fatigue was present, and in
what manner it influenced response; what were the effects of extremes
of temperature on the response; and, lastly, if chemical reagents could
exercise any influence in the modification of plant response, as
stimulating, anæsthetic, and poisonous drugs have been found to do
with nerve and muscle.
If it could be proved that the electric response served as a faithful index
of the physiological activity of plants, it would then be possible
successfully to attack many problems in plant physiology, the solution
of which at present offers many experimental difficulties.
With animal tissues, experiments have to be carried on under many
great and unavoidable difficulties. The isolated tissue, for example, is
subject to unknown changes inseparable from the rapid approach of
death. Plants, however, offer a great advantage in this respect, for they
maintain their vitality unimpaired during a very great length of time.
In animal tissues, again, the vital conditions themselves are highly
complex. Those essential factors which modify response can, therefore,
be better determined under the simpler conditions which obtain in

vegetable life.
In the succeeding chapters it will be shown that the response
phenomena are exhibited not only by plants but by inorganic
substances as well, and that the responses are modified by various
conditions in exactly the same manner as those of animal tissues. In
order to show how striking are these similarities, I shall for comparison
place side by side the responses of animal tissues and those I have
obtained with plants and inorganic substances. For the electric response
in animal tissues, I shall take the latest and most complete examples
from the records made by Dr. Waller.
But before we can obtain satisfactory and conclusive results regarding
plant response, many experimental difficulties will have to be
surmounted. I shall now describe how this has been accomplished.[7]
FOOTNOTES:
[2] In some physiological text-books much wrong inference has been
made, based on the supposition that the injured end is zinc-like.
[3] 'The exciting