THE PROBLEM OF BODY AND MIND 233 



made this admission we must advance to the other fact that 

 evolution of brains and evolution of behaviour have pro- 

 ceeded hand in hand, in intimate correlation. 



(c) The theory we frame as to the mind and body relation 

 must be consistent with the fact of their functional inter- 

 dependence. We express one side of this inter-dependence 

 when we say, " the spirit is willing, but the flesh is weak ", 

 which suggests the picture of a worn-out instrument unequal 

 to the player's demands. We express another side of the 

 inter-dependence when we say of our friend that " he died 

 in his prime, of a broken heart, having lost interest in life ", 

 which suggests the picture of a strong organisation or society 

 crumbling away because of the resignation of one who was 

 its heart and soul. 



A large and a complex brain among Vertebrates is cor- 

 related with a dominance of intelligent behaviour. The 

 more convolutions the greater the fulness and freedom of 

 life. An intricate brain among Arthropods is correlated 

 with subtlety of instinctive behaviour. Thus an important 

 part of the ant's brain is big in the worker, smaller in the 

 queen, and almost absent in the drone. Retardation or 

 warping of the development of the nervous system is as- 

 sociated with enfeeblement or disharmony of mental life. 

 Fatigue, or poisoning, or degeneration of the nervous system 

 has its mental correlate. Injury to particular areas of the 

 brain may bring about specific changes in behaviour, e.g., 

 disorders of speech. It seems, for instance, that an area 

 at the base of the third convolution on the left side of the 

 brain is the seat of the impressions and processes associated 

 with remembrance of the movements of articulation; that 

 an area affecting the first and second left temporal convolu- 

 tions is similarly associated with memory of the sound of 



