THE EVOLUTION OF THE BRAIN 



an infinite variety of delicately adjusted actions in the service 

 of the will, tlie eyes that see, the ears that hear, the hands 

 that feel — these and scores of other complicated pieces of 

 mechanism in the body are surely the mind's instruments, 

 such as in many other living creatures perform essentially 

 the same functions that they serve in man. But almost every 

 organ in the body plays a part in determining the appetites 

 and desires, the feelings and the thoughts. In ancient times 

 the Bible gave expression to the views then current among 

 men and attributed such influences to "the reins and the 

 heart" and to the bowels that were said "to yearn." Modern 

 science has revealed with greater precision the part each 

 organ plays (by means of its nervous connections as well as 

 by the "chemical messengers" or hormones it discharges into 

 the blood stream) in stimulating the dominant appetites and 

 affecting our feelings and emotions — in fact, in shaping our 

 behaviour. 



I have mentioned these conceptions merely to emphasize 

 the fact that no one organ or part of the body can be 

 regarded exclusively as the organ of the mind, seeing that 

 each and all, in their several fashions, may serve as instru- 

 ments in exciting or expressing human behaviour. But I 

 want to direct particular attention to the organ that plays 

 the dominant part in our mental life — the organ whereby 

 we are made aware of the sensory experiences that we call 

 sight, hearing, smell, taste, and touch and all the other 

 varieties of sensation, as well as of the feelings, appetites, 

 and sentiments. This organ, however, controls the compli- 

 cated reactions that find expression in behaviour. I do 

 not intend to discuss the nature of the relationship between 

 the activities of the brain and the phenomena of mind; my 

 purpose is to call attention only to certain well-recognised 

 facts and to discuss their meaning. We know that damage 



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