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 



