2 ORGANISM AND ENVIRONMENT 
regarded as a whole, it is evident that in the case of 
any given organism they are co-ordinated in such a 
way that the life of the organism tends to maintain 
itself as a whole, or at any rate to fulfil its character- 
istic life-history. This applies not less to the reactions 
between the organism and its environment than to 
those between the parts of the organism. In the 
inorganic world as ordinarily observed and inter- 
preted we find no such co-ordinated maintenance. 
How are we to understand its presence in the organic 
world? This is of course a very old question; but I 
wish to reconsider it in these lectures in the light, 
more particularly, of the very rapid advances which 
have been made during the last few years in the 
physiology of breathing. 
We are familiar with two opposing theories as to 
the nature of the co-ordination. One of these is that 
known as vitalism, which assumes that within the 
living body there is constantly at work a special influ- 
ence, the so-called “vital principle,” which guides the 
blind physical and chemical reactions which would 
otherwise play havoc with the organism. The other 
is that the body is a very complex and delicate 
mechanism, so arranged as to bring about the co- 
ordination. According to one school this mechanism 
is the result of natural selection, though according 
to another its origin must be sought in special creation. 
I hope to be able to convince you that neither the 
vitalistic nor the mechanistic theory of the relation 
between organism and environment is tenable, and 
