292 THEORETICAL BIOLOGY 



the impulse. The rule of shaping thereby becomes an impulse- 

 system, extended in space and influencing matter at different 

 places. We must now break up into a number of such systems 

 the protoferine that has not entered into the framework of 

 the cart ; and we shall find that the domain governed by 

 each system corresponds to the spatial extent of the part- 

 functions of the whole vehicle. Two impulse-systems, for 

 instance, would embrace the two wheels. At the common 

 axle, these would pass over into one another. Again, the 

 body of the cart, the seat, the pole, would each correspond 

 to one system. 



The several impulse-systems of the cart must in a measure 

 affect one another mutually, for at a number of points the 

 structures they govern fit into one another. At these points 

 the same protoferine will have demands made on it by two 

 impulse-systems. 



The impulse-systems have no direct influence on the run- 

 ning of the cart, since they are suited only for the production 

 of framework, and have lost all influence on the framework 

 itself. 



Even in those cases where, as in the ship, the compass is 

 not automatically connected with the rudder, but has to be 

 linked up with it anew as occasion requires, the steering 

 does not take place directly through a helmsman, but by 

 development of fresh mechanical connections between the 

 receptor and effector organs. We may imagine that the nerve- 

 meshes at the decisive points in the central nervous system get 

 linked up, now with one impulse-system and now with another ; 

 and this must result in a complete change in the reaction of 

 the whole animal. According to the number of impulse- 

 systems that lie ready to invade the central point, the 

 plasticity of the action will be greater or less. 



We can express this, indeed, in the formula for the plastic 



T^ . , , , R MOI AG E ., R MOI 



action. If mstead of j — — j — j we write j — 



