8/5 THE HOMEOSTAT 



v \j — y 



S 2 



Time 



Figure 8/5/1 : Three units interacting. At R the effect 

 of 2 on 3 was reversed in polarity. 



followed 2 downward (similar movement). 3 then forced 1 up- 

 ward, opposed the original movement, and produced stability. 



At R, the hand-control (2 — >■ 3) was reversed, so that 2 now 

 forced 3 to move in the opposite direction to itself. This change 

 set up a vicious circle and destroyed the stability; but uniselector 

 changes occurred until the stability was restored. A forced down- 

 ward movement of 1, at S 2 , demonstrated the regained stability. 



The tracing, however, deserves closer study. The action 2 — > 3 

 was reversed at R, and the responses of 2 and 3 at S 2 demonstrate 

 this reversal; for while at S ± they moved similarly, at S 2 they 

 moved oppositely. Again, a comparison of the uniselector- 

 controlled action 1 — > 2 before and after R shows that whereas 

 beforehand 2 moved similarly to 1, afterwards it moved oppo- 

 sitely. The reversal in 2 — > 3, caused by the operator, thus 

 evoked a reversal in 1 — > 2 controlled by the uniselector. The 

 second reversal is compensatory to the first. 



The nervous system provides many illustrations of such a series 

 of events: first the established reaction, then an alteration made 

 in the environment by the experimenter, and finally a. reorganisa- 

 tion within the nervous system, compensating for the experimental 

 alteration. The Homeostat can thus show, in elementary form, 

 this power of self -reorganisation. 



107 



