154 THEORETICAL BIOLOGY 



divides it up into organs. Where the physiologist analyses it 

 into sensory and motor apparatus, the biologist makes a corre- 

 sponding division into mark-organs and action-organs. 



The mark-organ includes the framework + protoplasm, in 

 so far as it serves for the creation of indications. The action- 

 organ comprises framework + protoplasm, in so far as it serves 

 for the creation of a definite movement-sequence, which we 

 call an action. 



Every time an indication appears, a function-rule lies 

 behind it, and comes to expression in the structure as well 

 as in the activity of the mark-organ. In the same way, a 

 function-rule lies behind every action, and finds expression 

 in the structure and the activity of the action-organ. From 

 this it follows that the actions of an animal can be closed 

 within a definitive function-rule. This may express itself 

 in an immutable framework, in which case an involuntary 

 action or reflex is created. Or the function-rule may make 

 the framework from time to time, as circumstances arise ; 

 then we get a protoplasmic instinctive action. Between 

 these two sorts of action come the so-called plastic actions, 

 among which actions based on experience are to be reckoned. 

 Finally, there are controlled actions, in which the function-rule 

 of the action-organ makes its determinative appearance even 

 in the mark-organ. 



The physiological analysis of a central nervous system is 

 finished, when the mark- and action-organs have been in- 

 vestigated. 



The biological analysis is finished, when the function-rules 

 for perception and for action are laid clear. 



