200 C. M. CHILD 
case of a part of an organism this change may be a change in 
physiological correlation resulting from changes in other parts, 
however produced. This change, external to the system concerned, 
produces an internal change of some sort in some part or parts, and 
this in turn alters the physiological correlation between the com- 
ponents of the system affected. So long as life continues, these 
correlative changes must result in equilibration in one way or 
another. The processes of equilibration may be very different in 
different cases: they may bring about sooner or later a return or 
approximation to the preéxisting condition—according to Driesch, 
this alone constitutes regulation and only when the preéxisting 
condition was the ‘normal’ condition. On the other hand, the 
correlative changes may result in the establishment of, or ap- 
proach to a condition of equilibrium more or less widely different 
from the preéxisting, and I believe that most, if not all regulations 
which we usually regard as an approach or return to the preéxist- 
ing condition actually represent an approach to a new equilibrium, 
often only slightly different from the old; it seems at least doubt- 
ful whether the organism ever really returns to a_ preéxisting 
condition in the strict sense. 
The new equilibrium may differ quantitatively or qualitatively 
from the old, or it may even result in the separation of the system 
into a larger or smaller number of systems, more or less completely 
isolated from each other. In all these cases, as the rate or character 
of the metabolic processes are changed, changes in structure as well 
as in function occur to a greater or less degree. The following 
suggestions for a classification of the regulatory processes are 
based primarily upon the metabolic processes concerned. 
3. <A provisional classification of the regulatory processes 
a. The two methods of regulation. It is evident that any really 
analytical classification which is based upon the conception of 
regulation sugg2sted above must take account, not merely of 
the visible features, but of the character of the different energetic 
processes, since regulation is, according to this view, essentially 
a complex of energetic processes in a substratum of a certain 
