110 ORGANISM AND ENVIRONMENT 
chemistry—an attempt which, in view of the facts of 
physiology can only end in certain failure. They 
assume as self-evident, for instance, that what they 
are dealing with is “living matter.” In reality these 
two words contradict one another. What we interpret 
as being in the sense ordinarily current, “matter,” 
cannot be also interpreted as living. 
Why has physiology failed to free herself from this 
misunderstanding? The fact of organic regulation 
has been evident enough from early times, and, except 
in more or less recent text-books, has received promi- 
nent attention from physiological writers. Various 
causes have, I think, contributed, and I should like now 
to refer to one which is specially prominent. 
The physiologists who laid most stress on organic 
regulation adopted the theory known as Vitalism— 
a theory which, though unorthodox, is still very much 
alive, and of which the eminent experimental embryol- 
ogist, Hans Driesch, is probably the best-known living 
representative. The vitalistic theory is that although 
matter and energy are, whether outside or inside of the 
body, just what current physical and chemical con- 
ceptions describe them as, yet in the living body they 
are guided by what older physiologists called the “vital 
spirit,” “vital force,” or “vital principle,” and what 
Driesch? calls “entelechy.” As is well known, Driesch 
discovered the fact that if the constituent cells of an 
embryo in its earliest stages of development are dis- 
1The clearest and shortest exposition of Driesch’s argu- 
ment is, I think, contained in his recent book, The Problem 
of Individuality, London, 1914. 
