564 WILL AND 



may now turn our attention more particularly to a con- 

 sideration of the parts whence, and of the channels 

 through which, Cerebral Incitations pass (on their way 

 down from cortical grey matter) in Emotional, Ideo-motor, 

 or Volitional Movements. 



One part of the route has been pretty clearly ascertained, 

 and this may be first referred to. 



From the evidence supplied by disease in the human 

 subject, from experiments upon some of the lower animals, 

 and from other sources of knowledge, it has been ascer- 

 tained that the Corpora Striata are great motor ganglia 

 in some way concerned with the execution of Voluntary, 

 Emotional, and Ideo-motor Movements. 



Motor stimuli that is stimuli which are to evoke 

 movements pass, therefore, from certain parts of the 

 Cerebral Cortex downwards to the corresponding Corpora 

 Striata. These bodies are called into activity in a way 

 which cannot be defined, though from them the motor 

 stimuli seem to be continued and redirected towards the 

 ' motor mechanisms ' of which we have previously been 

 speaking, in the Medulla and Spinal Cord. 



The tracks of these latter stimuli are fairly well known. 

 They pass from each Corpus Striatum through the inferior 

 layers of the Crus Cerebri, and through the Pons Varolii on 

 the same side ; whilst below this bridge they are gathered 

 together in the ' anterior pyramid ' of the Medulla, which, 

 after a course of a little more than one inch, decussates in 

 part with its fellow in such a manner that many of the 

 fibres of each pyramid pass over into the opposite ' lateral 

 column ' of the Cord,* whilst some continue to descend on 



* It would appear, from common phenomena occasioned by disease 

 of the great Nerve Centres in Man, that the cerebral channels 

 through which limb-movements, at least, are called into activity, 

 must undergo such a ' decussation/ 



