ii8 THEORETICAL BIOLOGY 



impulse-sequences, of which we never experience anything 

 directly, create the functions. Our knowledge of the schemata 

 may be extremely scanty, but we are still more in the dark 

 when it is a question of the functions ; for concerning the 

 exercise of the functions in every movement of the hand, in 

 every inclination of the head, and so forth, we learn some- 

 thing only through the medium of the sense-schemata, and 

 that thanks to the direction-signs connected with those 

 movements. 



We have no direct knowledge whatsoever of what we do 

 quite as a matter of course. What we learn with regard to 

 all our actions comes from the sense-signs alone, which serve 

 to control our movement. 



This is why it is so extremely difficult to get deaf-mutes to 

 speak, for they lack control by the ear, and the laryngeal 

 musculature has no direction-signs. Only by calling in the 

 assistance of the direction-signs of mouth and tongue do we 

 succeed in impressing on deaf-mutes certain indications, which 

 they can use in producing sounds. Learning to read and 

 write, on the other hand, presents no greater difficulties to 

 them than it does to normal people. 



The case of deaf-mutes gives us a good idea of what our 

 complete helplessness would be if we were deprived of the 

 sense-control of our actions. We should actually be incapable 

 of initiating even the least regulated sequence of movements. 



In the case of animals it is not possible to make this state- 

 ment. There are animals that execute quite definite move- 

 ment-sequences, in which control by the sense-organs is 

 lacking. Actions of this kind can come about through a 

 special kind of nerve-linking ; they are called reflexes. When, 

 on the other hand, regulated movement-sequences are per- 

 formed by an animal that is without control by sense-organs, 

 4 and such movements are not linked together and conditioned 

 by any demonstrable structure, we speak of instinctive actions. 



