DESIGN FOR A BRAIN 



15/10 



of eyes, muscles, skin-receptors, some parts of the brain, and hard 

 external objects is stable and always acts so as to keep within 

 limits the mechanical stresses and pressures caused by objects in 

 contact with the skin-receptors (S. 5/4). The diagram of immedi- 

 ate effects will therefore resemble Figure 15/10/1. This system 

 will be referred to as part A, the ' avoiding ' system. 



BRAIN -«- 



EYES 



SKIN 



MUSCLE S 



^-OBJECTS 



Figure 15/10/1 : 

 system. 



Diagram of immediate effects of the ' avoiding ' 

 Each word represents many variables. 



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

 develop a set of values on step-me'chanisms 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 normal limits. (This system will be referred to as part B, 

 the ' 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 within brain 

 and environment may allow the two reactions to use common 

 variables. When the systems interact, the diagram of immediate 

 effects will resemble Figure 15/10/2. 



BLOOD 



glucose' 



-^- BRAIN -<- 



f 



FOOD . 

 SUPPLY "*" 



V 



EYES 



SKIN 



V 



MUSC LES 



— >OBJECTS 



B A 



Figure 15/10/2. 



Let us assume at this point (simply to get a clear discussable 

 case) that the step-mechanisms affecting A are, for whatever 

 reason, not changeable while the adaptation to B is occurring 

 (compare S. 10/8). As the ' avoiding ' system A is not subject 



202 



