VISION. 



553 



It is of great importance to recognize that what we really 

 see depends more upon the brain and the mind than the eye. 

 If any one will observe how frequent are his incipient errors 

 of vision speedily corrected, he will realize the truth of the 



Brain above 

 medulla 



Centre In region of- 

 corp, guadrigemina 



-Corneal centre 



— j-Centre in optle tJialamua 



leUna 



Fig. 400. — Diagram intended to illustrate the elabdi-ation of visnal Impulses, beginning 

 in retina and culminating in the cerebral cortex. Course of impulses is indicated 

 by arrows. Knowledge of auditory centers is not yet exact enough to permit of 

 the construction of a dia^am, though doubtless eventually the central processes 

 will be localized as with vision. The latter remark applies to the other senses to 

 nearly the same extent, possibly quite as much. 



above remark. Precisely the same data furnished by the eye 

 are in one mind worked up in virtue of past experience (edu- 

 cation) into an elaborate conception, while to another they an- 

 swer only to certain vag^e forms and colors. And herein lies 

 the great superiority of man's vision over that of all other 

 animals. 



Within the limits of their mental vision do all creatures see. 

 Man has not the keen ocular discriminating power of the hawk; 

 he can neither see so far nor so clearly ; nor has he the wide 

 field of vision of the gazelle ; but he has the mental resource 

 which enables him to make more out of the materials with 

 which his eyes furnish him. It is by virtue of his higher cere- 

 bral, development that he has added to his natural eyes others 



