CH. xvi.] THE EVOLUTION OF MIND. 137 



ments made in the trunk and limbs are effected either 

 directly by the spinal centres, or indirectly by the sympa 

 thetic ganglia in cooperation with the spinal centres. The 

 medulla coordinates all these muscular adjustments with the 

 muscular adjustments of the face, and with the impressions 

 received from the specialized organs of sense. It is therefore 

 highly improbable that the supreme ganglia can be in any 

 wa} T directly concerned with these coordinations. And the 

 improbability is increased by the fact that the cerebrum and 

 cerebellum are as destitute of sensation as the free ends of 

 the ringer-nails. Scratch one of the spinal centres, and the 

 result is tetanus. Scratch the medulla, and the whole body 

 is thrown into terrible convulsions. But the cerebrum and 

 cerebellum may be scratched and sliced without pain or con 

 vulsion. They take heed only of those impressions which 

 are communicated to them indirectly. Countless multitudes 

 of nerve-fibres coming up from the medulla, are gathered 

 together in the corpora striata ; whence other fibres, con 

 tinuing from them, radiate to the innumerable cells of which 

 the supreme ganglia are composed. 



We must conclude, therefore, that the functions of the 

 cerebrum and cerebellum are comprised in the further com 

 pounding of sensory impressions already compounded in the 

 medulla. And as such compounding involves the repro 

 duction of impressions received in lower centres, and also 

 involves the coordination of past with present impressions, 

 we may say that the supreme ganglia are the seats of the 

 higher psychical life, of memory, reason, emotion, and voli- 

 tiun. Dr. Mauds-ley has thus appropriately termed them the 

 id -ational centres. But between the functions of the two, 

 thus closely related, there is nevertheless a difference. 

 Although the precise determination of the way in which 

 ideational functions are shared between the two centres, has 

 long remained a puzzling problem, there is good reason for 

 believing that Mr. Spencer has solved the difficulty by 



