PHYSIOLOGICAL BASIS OF PATTERN 31 
lower range of concentrations or intensities, also experi- 
mentally determined for each species, the rate and 
degree of acclimation or acquirement of tolerance varies 
directly with, though not necessarily proportionally to, 
the general physiological activity of the protoplasm, 
and the rate and degree of recovery after temporary 
exposure to the action of the agent also varies in the 
same way. The metabolic reactions and particularly 
the oxidations are important factors in the general 
physiological activity of protoplasm, and many lines of 
evidence show that susceptibility may be used, within 
certain limits and with certain precautions, as a rough 
comparative measure or indicator of the rate of oxida- 
tion. This of course does not mean that all the agents 
used in determining susceptibility act directly on the 
oxidations. Undoubtedly different agents act in very 
different ways upon living protoplasm, but the general 
nonspecific character of the susceptibility gradients 
demonstrated with many different agents indicates the 
interrelation of different processes and conditions in the 
protoplasmic system. The difference between a region 
of high and one of low rate of oxidation unquestionably 
involves not simply the oxidative reactions but many 
other factors, e.g., colloid dispersion, permeability of 
limiting surfaces, active mass of enzymes, etc., and 
within physiological limits change in the physiological 
state involves changes in all these and doubtless other 
factors. Apparently the general relation between sus- 
ceptibility and physiological state is primarily an 
expression of the fact that the dynamic equilibrium of 
the more active state is, on the one hand, more readily 
upset by any extreme external action than that of the 
