Medical Officers of the Army of India.
one thing which cannot fail to strike any one who is in any degree acquainted
with the subject, namely, that in the experiments in regard to which details are
here given, the extension of the action under the influence of so-called stimulant
agencies, such as section and heat, is curiously limited as compared with what
it would appear to be in Europe according to the ordinarily accepted authorities.
Now, there can be absolutely no doubt that this limited extension is the normal
phenomenon in plants grown in the, open ground in Calcutta under similar con-
ditions to those to which the plants of the experiments were exposed. But if
this be so, the difference in degree of propagation of movement in Calcutta and
Europe must be due either to differences in the degree of irritability, conduc-
tivity or contractility of the protoplasm of the tissues, or to the presence of
differences in degree of conditions favouring the occurrence of fluctuations in
degree of fluid tension throughout the tissues. According to the former view
it must be assumed that in the plants in Calcutta growing in the open ground
and under conditions so favourable as to lead them to run wild and assume the
character of troublesome weeds, the protoplasm is less irritable, or less conduc-
tive or less contractile than it is in pot-plants in European laboratories and
conservatories. The necessities of the theory remain, however, the sole ground
for any such assumption. On the other hand, on the view that the propagation
of movements is essentially due to extension of fluctuations in tension of fluid in
the tissues, an explanation of the phenomenon is ready at hand. In plants
growing as they do in Calcutta, the facilities for rapid and extensive root ab-
sorption must be much greater, and the tendency to loss by evaporation much
less than in plants with roots confined within limited areas of soil in pots and
exposed to the relatively dry air of laboratories or conservatories. 1 Any inter-
ference giving rise to abnormal escape of fluid from the tissues either as the
result of ruptured continuity as in cases of section, or of diminished capacity to
retain fluid, such as is apparently present (vide page 95) in cases of heating, must
almost inevitably give rise to movements, the extension of which over larger
or smaller areas of the tissue will be proportionate to the facilities for rapid
removal of fluid from the. site of escape and for a renewed supply to make good
the loss. In plants under conditions such as those prevailing in Calcutta we
should expect, then, to find, what we actually do find, that extensive propagation
of movement is a rare phenomenon as compared with what it is in European
plants. It appears thus that in this instance the theory of propagation of
movement as essentially dependent on protoplasmic continuity fails to furnish
an explanation of a phenomenon readily explicable by the other view, and that
this phenomenon is one indicating that the extension of movement is propor
tionate to extension of fluctuations in fluid contents of the tissues.
' In Calcutta, as in the lower parts of the Gangetic delta generally, we have to deal with an area in
which the soil is at all times saturated to within a few feet of the surface, the atmospheric humidity con.
stantly high and frequently excessive, and the rainfall great.
87