98 CONSCIOUSNESS AND SENSATION. 



and suppose them to exist in the fibres of the cord 

 alone, we assume that the work which requires a 

 whole fibre in a peripheral nerve, can be done by 

 one of a multitude of striae in a fibre of the cord, 

 which seems improbable. 



If the difficulties which have been enumerated 

 appear great, when the received theory is applied 

 to the explanation of common sensation, they are 

 still more striking when it is applied to vision. 

 The theory demands that for every ray of light 

 appreciated by the mind there must be a com- 

 pletely distinct communication from one of the rods 

 or cones which constitute the individual sensory 

 organs of the retina to a terminus in the brain, 

 and that the impressed condition of every such 

 terminus must be capable of creating in the mind 

 a knowledge of the position of the point on which 

 the ray falls as related to all the other impressed 

 points of the retina. That supposition involves 

 all the difficulty which has been pointed out in the 

 case of common sensation ; while the anatomy of 

 the retina, even more distinctly than that of the 

 spinal cord, contradicts the possibility of distinct 

 communication between each of the immense num- 

 ber of peripheral nerve-terminations and the seat of 

 consciousness. Within the retina, the threads 

 leading from the terminal rods and cones already 



