CONSCIOUSNESS AND SENSATION. 107 



existence of distinct routes, as has hitherto been 

 done. 



Let it be distinctly understood that I do not say 

 that consciousness resides in the nerve-extremities, 

 but only that when the nerves are in the active or 

 impressed condition in their whole extent up to 

 the brain, the consciousness is affected directly 

 by the irritations applied to their extremities. 

 The relation then of consciousness to the brain 

 remains totally different from its relation to the 

 nerve. The impressed condition of the cerebral 

 corpuscles produces only excitement of the mind ; 

 the impressed condition of a peripheral nerve or 

 its extremity continued up to the brain brings 

 the consciousness into communication with the 

 irritation applied. 



At the extremities of the different nerves are 

 placed various arrangements which are least com- 

 plicated in the nerves of general sense, and which 

 modify their capability of being irritated by differ- 

 ent stimuli. Thus the expansion of the optic 

 nerve is incapable of being affected by the irritation 

 of light, but the rods and cones of the retina are 

 irritated by them with ease. The complicated 

 nerve-extremities of the ear are acted on by sounds, 

 and the comparatively simple extremities of the 

 nerves of general sense are acted on by mechanical 



