506 THE SENSORIAL FUNCTIONS. 



fibres, passing directly across from one side of 

 the brain to the other, has been provided ; these 

 constitute what are called the Commissures of the 

 Brain. 



The question, however, still recurs ; — What rela- 

 tion does all this artificial intertexture and accu- 

 mulation of fibres bear to the mental operations 

 of which we are conscious, such as memory, ab- 

 straction, thought, judgment, imagination, volition ? 

 Are there localities set apart for our different ideas 

 in the store-house of the cerebral hemispheres; 

 and are they associated by the material channels 

 of communicating fibres ? Are the mental pheno- 

 mena the effects, as was formerly supposed, of a 

 subtle fluid, or animal spirits, circulating with great 

 velocity along invisible canals in the nervous sub- 

 stance ; or shall we, with Hartley, suppose them 

 to be the results of vibrations and vibratiuncles, agi- 

 tating in succession the finer threads of which this 

 mystic web has been constructed? A little reflec- 

 tion will suffice to convince us that these, and all 

 other mechanical hypotheses, which the most fan- 

 ciful imagination can devise, make not the smallest 

 approach to a solution of the difficulty ; for they, in 

 fact, do not touch the real subject to be explained, 

 namely, how the affections of a material substance 

 can influence and be influenced by an immaterial 

 agent. All that we have been able to accomplish 

 has been to trace the impressions from the organ 

 of sense along the communicating nerve to the 

 sensorium : beyond this the clue is lost, and we 

 can follow the process no farther. 



The exact locality of the sensorium has been 



