364 Ewart . — The Action of Cold and of 
influences may directly affect single functions only or these 
in more marked degree than in others, but in every case, 
even if only a single function is directly affected, an indirect 
effect must finally be produced upon all the other functions, 
provided the stimulus affecting the first function acts for 
a sufficiently long period of time. This is a necessary 
corollary to the intimate connexions and correlations which 
exist in the living organism between its different functional 
activities. 
In laboratory experimentation we make use of these 
principles, the effects produced on single functions being 
noted in plants kept under otherwise normal conditions, 
while at the same time the direct and indirect effects pro- 
duced are as far as possible distinguished from one another. 
Having obtained a knowledge of the action of the different 
factors constituting the external world upon each particular 
vital function, the next thing necessary is to submit the 
results thus obtained to the test of nature, by which they 
must stand or fall. If, however, the observations made in 
nature do not coincide with the results obtained by laboratory 
experiment, it does not necessarily follow that either are 
incorrect. The discrepancy between the two may simply 
indicate that in either or both cases certain operating factors 
have not been noticed or allowed for. 
It is therefore as absurd for the biologist to deride the 
results obtained by laboratory experimentation, as it would 
be for the physiologist to disregard the criticisms and limita- 
tions which the biologist imposes upon him. Only by giving 
to each their proper value and importance can the facts 
observed by the biologist and physiologist be correlated 
and brought into harmony with one another 1 . 
Bearing these facts in mind, I proceed to discuss certain 
points in the paper by Messrs. West, to which the above 
disquisition appears to be especially applicable. In the 
1 An admirable general account of these and similar questions is given in the 
introduction to Pfeffer’s new Pflanzenphysiologie. (An English translation is in 
process of preparation for the Clarendon Press.) 
