OF MIND AS A FUNCTION OF THE BRAIN. 137 



are changed. The function of a muscle is to contract and 

 become relaxed, but the material change only occurs in 

 definite directions, necessitated by the structure of the 

 instrument and the force which acts upon it. The exercise 

 of choice is neither possible nor conceivable. So, too, with 

 reference to the function of nerves. These transmit cur- 

 rents. The paths which the currents are to traverse having 

 been determined and formed, the currents are developed 

 and transmitted along the nerves. 



But the discharge of function on the part of the organ 

 of the mind is an operation very different from any of these. 

 The great characteristic in this case is choice selective 

 capacity. If the cells of the liver chose for themselves 

 whether they would secrete bile or not, or determined the 

 kind of bile to be secreted, or the bile chose for itself by 

 which ducts it should pass, whether it would flow quickly, 

 slowly, or not at all ; if the muscle contracted now in one 

 part and now in another, according as it willed if it 

 elected to contract in one direction, and then in a different 

 one ; if the nerve cells decided among themselves which 

 should produce current and which not : if the current chose 

 to run along one fibre at one time and then along another, 

 according to the object it had in view then, but only then, 

 as it seems to me^ could mental activity be regarded as in 

 any way analogous to the function of an organ or of a tissue. 

 To look upon mental action as a mere function of the brain 

 seems to be a fundamental error, and one which those who 

 have really studied the structure and action of secreting 

 organs and nerve organs could not make. 



Mental activity may rather be compared with that mar- 



