108 ORGANISM AND ENVIRONMENT 
in the same way as the physicist or chemist would pro- 
ceed. This method yields much provisional informa- 
tion for further investigation and more correct inter- 
pretation, through which real physiology advances; 
and the mere possession of the provisional informa- 
tion is itself of great value. By showing that the living 
body could in certain respects be regarded as a heat- 
producing machine Lavoisier made a great step for- 
wards, though he did not realise that the heat-produc- 
tion is organically regulated. For an animal in normal 
environment the hypothesis that there is a constant 
relation between intake of energy in the form of free 
oxygen and food-material, and output of energy as 
heat and in other forms, has stood the test of the most 
rigorous experiments. The fundamental observations 
of Regnault and Reiset, Pfltiger, Rubner, and others 
have, however, shown that both intake and output of 
energy are strictly regulated, like other physiological 
activities ; and what is implied in this organic regula- 
tion has already been discussed. The preliminary 
comparison of the organism to an energy-transforming 
machine has been of great value in certain directions, 
but has misled, and still continues to mislead, physiolo- 
gists in others. The real source of the misunder- 
standing has been the assumption that physical and 
chemical working hypotheses are more than working 
hypotheses of limited profitable application, and accu- 
rately correspond to reality itself. 
This assumption has given rise to the mechanistic 
theory of life as a necessary corollary, as well as to 
all that is vaguely designated as “materialism.” But 
