ORGANIC RESPONSE 253 



Some biologists believe that the majority of reac- 

 tions to stimuli, such as light, heat, diffusion of 

 chemicals, electricity, etc., are based upon some such 

 automatic mechanism. We should be very cautious, 

 in any event, in interpreting such movements in 

 terms of human experience, and ascribing choice 

 and volition to organisms that exhibit such a response. 

 On the other hand, the careful study of the behavior 

 of a number of microorganisms has shown that the 

 same individual will not react at all times in the 

 same way to the same stimulus, which it would be 

 compelled to do if the response were absolutely 

 mechanical. The nature of the response is depend- 

 ent upon the " physiological state " of the organism 

 at the time of stimulation. But this does not mean 

 that such responses are purposive, even if they are 

 to the advantage of the organism possessing them. 



Adaptive Response. - - We are familiar with many 

 ways in which our own bodies accommodate them- 

 selves automatically to environmental change. The 

 greater demand we make upon a muscle, the more the 

 muscle increases and grows to meet that demand. 

 Those parts of the skin which are exposed to friction 

 develop horny, protecting calluses. If, through 

 disease, one kidney becomes ineffective or function- 

 less, the remaining one grows larger (hypertrophy) in 

 order the better to carry out the double burden laid 

 upon it. These examples indicate how very plastic 

 even such an organism as highly specialized man 

 may be. The changes mentioned, and many other 



