294 THEORETICAL BIOLOGY 



■p 



J, for example, means a receptor — an eye, let us say, — 



together with all its protoplasm and the impulse-system 

 governing that. To the eye also belong the nervous connect- 

 ing-routes to the mark-organ. But, on the other hand, these 

 belong to the mark-organ itself. Here, therefore, is the de- 

 batable ground, which is under the control of two impulse- 

 systems. 



y means the mark-organ of the central nervous system, 



with its protoplasm and the governing impulse-system, etc. 

 But everywhere the connecting-routes from one organ to the 

 next are the integrating portions of each one. The functional 

 building-stones of which the reflex arc is made up, every- 

 where interlock with one another. In how far the impulse- 

 systems interlock can be decided only by experiment. As 

 concerns the motor nerves going from the action-organ to the 

 muscles, the experiment of severing the nerves has shown 

 that they belong to the impulse-system of the action-organ, 

 for from that organ the nerves grow out again to the muscle 

 after the severance. The impulse-system of the action-organ, 

 and not that of the muscle, is responsible for the repair to 

 the nervous connections. 



The uncertainty concerning the delimitation of the func- 

 tional building-stones one from another exists from the 

 moment beyond which one can speak of functional building- 

 stones at all, i.e. from the critical point onwards. 



Up to the critical point there is in the animal body no 

 connecting function, and consequently there are no functional 

 building-stones. Until the critical point is reached, the body 

 is divisible into germinal areas, which I have called genetical 

 building-stones. 



In order to make quite clear the rearrangement that takes 

 place at the critical point, let us assume that, in some selected 

 animal, the critical point comes on through the whole body 



