18 THE DOCTRINE OF DESCENT. 
the atoms, is likewise included in the incomprehensi- 
bility of matter. 
“If we pass over this,” says Dubois-Reymond again, 
“the universe is approximately comprehensible, Even 
the appearance on the earth of life in the abstract does 
not render it incomprehensible. For life in the abstract, 
contemplated from the standpoint of the theoretical 
investigation of nature, is merely the arrangement of 
molecules in a state of more or less stable equilibrium, 
and the introduction of an exchange of material, partly 
by their own elastic force, partly by motion trans- 
ferred from without. It is a misapprehension to see 
anything supernatural in this.” 
This is the point which is usually contested with the 
greatest vehemence, If all the motions and states of 
quiescence of the inanimate world can be thoroughly 
explained, the inexplicable must commence with the 
basis of life. The imputation cast upon the reasoning 
powers by this assumption may be formularized as 
follows, in the question put by another sound and 
thoughtful physiologist, A, Fick:* “Are the charac- 
teristics of such a particle, as already explained, 
applicable and effective during the period of its sojourn 
in an organism? Thus, for instance, will the motions 
of a particle of oxygen be affected and altered by a 
neighbouring particle of hydrogen, in accordance with 
the same laws, when one or both form part of an 
organism, as when they are out of it ?” 
To reply in the negative is to avow the vitalistic 
conception of life, that is, to take refuge in unknown 
forces quite extraneous to matter, and to admit that 
the self-same particle can vary its nature, according 
