458 Edward Livingston Youmans. 



they had hitherto been assigned — was a signal event in the 

 progress of physiological inquiry, as it quickly led to the 

 extension of the principle of automatism to the cerebrum 

 itself. This portion of the brain is now regarded as the 

 organ of all the higher mental activities — the seat of. ideas 

 and of the complex intellectual operations, memory, imagina- 

 tion, reason, volition. The most obvious case of reflex 

 cerebral action is where a remembered or suggested idea 

 produces a spontaneous movement. Thus the recollection 

 of a ludicrous incident may excite an involuntary burst of 

 laughter, the remembrance of a disgusting taste may cause 

 vomiting. When ideas are associated with pleasure or 

 pain, a class of powerful feelings is produced — the emo- 

 tions, which become the springs of impulsion, or reflex 

 activity. Those bursts of movement which are peculiar 

 to the various emotions, as anger, terror, joy, and which 

 we term their expressions ^ are examples of cerebral spon- 

 taneity. 



These facts prepare us to understand the scope and 

 limits of voluntary activity, the function of which is to 

 restrain the impulsive tendencies, and direct the bodily 

 movements to various ends. In voluntary action the will 

 does not replace or dispense with the involuntary system, 

 but rather uses it. Its action is limited by the laws of the 

 vital mechanism with which it works. Of all the number- 

 less movements going on in the organism, volition has con- 

 trol only of the muscular, and of these but partially. It 

 cannot act directly upon the muscles, but liberates nerve 

 force in the brain, which in turn produces muscular con- 

 traction. The voluntary powers determine the e?id to be 

 accomplished, and employ the automatic system to execute 

 the determination. I will a given action, and of the many 

 hundred muscles in my system, a certain, and perhaps a 

 large number, will be called into simultaneous exercise, re- 

 quiring the most marvellous combinations of separate ac- 



