178 Cc. M. CHILD 
‘living substance’ in the stricter sense, but are really the least 
‘alive’ of any part. The reactions which furnish the energy of 
life undoubtedly occur, at least in large measure, in the more fluid 
parts of the cell, the parts which present the least characteristic 
structure. The so-called living substance is actually then, so far 
as it presents a visible structure, chiefly a substratum or medium 
in which the reactions occur, and is itself the product of past reac- 
tions. That these structural elements, as they accumulate, must 
modify the rate and character of the reactions to an increasing 
extent, cannot be doubted. The advancing specialization of 
metabolism in different organs and cells is probably closely con- 
nected with the fact that these parts produce different structural 
elements, either in consequence of an original specification or 
in consequence of different correlative or external conditions which 
induce specification. . 
If we accept this view of the relation between function and 
structure in the organism, we must give up the idea of a definite 
‘living’ substance in the chemical sense, and the basis of life 
becomes, not a specific substance, but a series of reactions ina 
field or medium of a certain complex constitution, which is itself 
the product of past reactions. We can agree with Driesch (01, 
p. 140), as regards the absence of aspecific living substance, though 
we cannot follow him in his further conclusions along this line. 
The life process has become individualized, not because of entele- 
chy, but because it forms its own field or medium of action, as the 
river forms its channel, particularly in the later stages of its course, 
where deposition exceeds erosion. To put the matter briefly, 
life as we know it consists not in metabolism alone nor in a speci- 
fic substance or structure alone, but in the physiological correla- 
tion of processes in a structural medium or substratum of a cer- 
tain constitution, which makes possible localization and correla- 
tion of processes. . 
It is then the existing relation between the processes and the 
structural substratum, the mutual interaction and dependence of 
both, that forms the basis for the phenomena of regulation or 
equilibration which occur in the organism. 
