332 The Vital Phenomenon: Assimilation 
as we have affirmed before, can help to explain in great 
part the essential character of the vital phenomenon itself 
in all its generality—that is assimilation. 
The fact that strikes us first of all is, that the vital 
phenomenon depends upon continual reproduction, for 
assimilation constantly reproduces the substance which is 
gradually consumed. It is to be expected therefore, that 
if there are any fundamental properties of living organic 
substance which explain the phenomena of development 
or of reproduction in general, they must then be capable 
of accounting for assimilation also, inasmuch as it is 
itself a phenomenon of reproduction. 
That being granted it will be worth while that we 
next stop for an instant to take a look at and consider 
briefly a few of the principal conceptions which biologists 
have put forward on the nature of either the vital phe- 
nomen or of assimilation, and which are of the greatest 
interest from our point of view. 
Roux, for example, rightly urges that the nature of 
life must be dynamic. “Life is in its essence a process, 
and cannot therefore have a static definition. It is 
therefore only a processive and consequently functional 
definition which can approximate the essence of organic 
hte, #22 
On the other side we have already seen the reasons 
for concluding that the essence of the vital phenomenon 
consists in an activation of nervous energy. We re- 
call that according to Orr for example, the funda- 
mental property of living substance is an “elemental 
nervousness.” 75° 
*°Roux: Uber die Bedeutung der Kernteilungsfiguren. Leipzig, 
Engelmann, 1883. P. 18. Gesamm. Abhandl. Bd. II. P. 142. 
*°Orr: A Theory of Development and Heredity P. 86. 
