17/5 



DESIGN FOR A BRAIN 



As the animal must now get its own food, the brain must 

 develop a set of step-function values that will give a field in which 

 the brain and the food-supply occur as variables, and which is 

 stable so that it holds the blood-glucose concentration within 



BRAIN -«- 



EYES 



SKIN 



MUSCLE S 



-^OBJECTS 



Figure 17/5/1 : Diagram of immediate effects of the ' avoiding ' 

 system. Each word represents many variables. 



normal limits (S. 5/6). (This system will be referred to as part B, 

 the 4 feeding ' system.) This development will also occur by 

 ultrastability ; but while this is happening the two systems will 

 interact. 



The interaction will occur because, while the animal is making 

 trial-and-error attempts to get food, it will repeatedly meet 

 objects with which it might collide. The interaction is very 

 obvious when a dog chases a rabbit through a wood. Further, 

 there is the possibility that the processes of dispersion may allow 

 the two reactions to use common variables. When the systems 

 interact, the diagram of immediate effects will resemble Figure 

 17/5/2. 



BLOOD 

 GLUCOSE" 



-^~ BRAIN -<- 



EYES 



FOOD 

 SUPPLY 



V 



SKIN 



-«- 



y 



MUSC LES 



B 



^-OBJECTS 



Figure 17/5/2. 



As the * avoiding ' system A is not subject to further step- 

 function changes, its field will not alter, and it will at all times 

 react in its characteristic way. So the whole system is equivalent 

 to an ultrastable system B interacting with an ' environment ' A. 

 B will therefore change its step-function values until the whole 

 has a field which is stable and which holds within limits the variable 

 (blood-glucose concentration) whose extreme deviations cause the 

 step-functions to change. We know from S. 8/10 that, whatever 

 the peculiarities of A, B's terminal field will be adapted to them. 



188 



