CHAP, ii.] THE BRAIK 773 



dition that the application of even a momentary stimulus to an 

 area leads not to a simple movement but to a long-continued 

 tonic contraction of the appropriate muscles. Under these cir- 

 cumstances, a gentle stimulus, such as stroking the skin, or blow- 

 ing on the face, applied immediately after the application of the 

 electric stimulus to the area, suddenly cuts short the contraction, 

 and brings the muscles at once to rest and normal flaccidity. 



490. The carrying out of a voluntary movement is in fact 

 a very complex proceeding, and the motor cortex with the pyra- 

 midal tract is only one part of the whole mechanism. This 

 complexity is illustrated by the fact that after removing of a 

 motor area not only purely voluntary but also reflex and other 

 movements are for a while abolished or impaired; and even 

 making every allowance for the effects of c shock ' ( 457) we 

 cannot account for the latter to the exclusion of the former, by 

 appealing to such effects. It is further shewn by the fact that 

 in the case of most voluntary movements at least, after removal 

 of an area recovery is after a while complete, though there is no 

 regeneration either of the area or the strand of the pyramidal 

 tract belonging to it ; the will finds some other way to the 

 muscles and to mechanism coordinating the movements of those 

 muscles. By the following reflection the complexity of the 

 matter is also shewn in a different direction. When a gymnast 

 executes a skilled voluntary movement in which all his four 

 limbs and other parts as well perhaps of his body are involved, 

 it is probably the case that changes of the nature of efferent 

 impulses sweep down his pyramidal tract, and that these im- 

 pulses, starting in a definite order from his cortex, that is to say 

 having undergone a certain amount of initial coordination at 

 their very origin, meet with further coordination in the spinal 

 grey matter, which serves as a set of nuclei of origin for the 

 motor nerves concerned in the movement, before they issue as 

 ordinary motor impulses along the anterior roots. But this is 

 not all. Should the gymnast's semicircular canals happen to be 

 injured and his cerebellum thereby be troubled, or mischief fall 

 on some other part of the brain which like this has no direct 

 connection with either the pyramidal tract or the motor cortex, 

 the movement fails through lack of coordination, though both 

 the cortex, the pyramidal tract, and the spinal motor mechanisms 

 remain as they were before. 



Lastly we may note that in the above discussion we have 

 used the word ' will ' in a general sense only. A man may be 

 brought into a condition, for instance in certain hypnotic phases, 

 in which he can carry out all the various skilled movements which 

 he has inherited or which he has learnt ; and yet, according to 

 some definitions of the word ' will,' those movements could not 

 be said to be initiated by his will. It can hardly be doubted 

 that in such cases the motor cortex and pyramidal tract play 



