17/4 



ANCILLARY REGULATIONS 



For the co-ordination to occur, there must be some channel 

 from the source of the left arm's variations to the right arm's 

 movements (/. to C, S. 11/11; the pairing proves as much by 

 S. 4/13 above). Our question now is: must this channel lie within 

 the brain ? 



Not only it need not, it usually does not; as the following 

 argument will show. Consider the situation at the moment when 

 the ball is in mid-air: is the right arm's developing movement 

 now guided by messages from the left arm's centre* or from the 

 position of the ball in the air ? The operational test (of S. 4/12 

 and 12/3) is decisive : let the left arm's movements remain unaltered 

 but assume now that the position of the ball be altered, by a sharp 

 gust say; is the right arm's movement altered? The normal 

 player, if the ball should be affected by a gust, will at once modify 

 his right-arm movements accordingly. These modifications, by 

 the basic operational test, show that the right arm is immediately 



ORGANISM 



Figure 17/4/1. 



* We must avoid the tangles caused by the fact that the right arm is 

 controlled by the left motor cortex, and vice versa. 



221 



