AUTOMATIC MOTIONS. 225 



ing to it sensational changes whereby its peculiar 

 sensation, as an instrument of purely mental oper- 

 ations, is called forth ; and in return the cerebrum 

 appears to play downwards upon the motor por- 

 tion of the automatic apparatus, sending to it 

 volitional impulses which excite its motorial ac- 

 tivity. And hence it follows that all the move- 

 ments which are performed by the instrumentality 

 of the cerebro-spinal nervous system are in them- 

 selves automatic ; and that the peculiarity in their 

 character whether excitor, motor, consensual, 

 ideational, emotional, or voluntary is due to 

 the speciality of the source and seat of the im- 

 pulses which respectively originate them." ' 



We may assume that the continuous periodic 

 motion is one and the same as the continuous 

 automatic movement ready to be " played upon " 

 by the will ; and the " speciality of the source and 

 seat of the impulses " to be the distinctive nervous 

 arrangement peculiar to each individual organ. 



1 Carpenter's Comparative Physiology, p. 688. 



