2 8o Journal of Comparative Neurology and Psychology. 



of the walls of the brain, may be supposed to convert the complex 

 etimuli into an element of cortical reaction capable of taking a place 

 in the equilibrium directly. There is certainly much in the structure 

 of the retina to suggest coordination of a high order, rather than the 

 view that the sole function is to transmit the stimuli direct to the brain, 

 and it is not improbable that the ganglia serve to impress upon stimuli 

 their specifically op/ic character. The existence of centripetal fibers 

 suggests accommodation processes in the retina itself. 



But none of these suggestions removes the mystery as to what 

 actually passes over the optic nerve when we see. If a simple kind of 

 chemical reaction formed by the vibration of n'/wlc light produces a 

 white sensation, there seems to be no reason to suppose that the other 

 chemical process resulting from the mingling of various fractional light 

 vibrations should go to the brain or receiving center as discrete stimuli 

 each to produce a sensation, which separate sensations now unite to 

 form a composite sensation, say of purple. We know no such psycho- 

 logical process as this. Each color sensation is complete and discrete 

 in itself. c. L. herrick. 



