THE PERCEPTION OF SIGHT. 275 



tion of a word, even when it is used exceptionally in some other 

 sense; we cannot help feeling the mental emotions which a 

 fictitious narrative calls forth, even when we know that it is not 

 true ; just in the same way as we cannot get rid of the normal 

 signification of the sensations produced by any illusion of the 

 senses, even when we know that they are not real. 



There is one other point of comparison which is worth notice. 

 The elementary signs of language are only twenty-six letters, 

 and yet what wonderfully varied meanings can we express and 

 communicate by their combination ! Consider, in comparison 

 with this, the enormous number of elementary signs with which 

 the machinery of sight is provided. We may take the number 

 of fibres in the optic nerves as two hundred and fifty thousand. 

 Each of these is capable of innumerable different degrees of 

 sensation of one, two, or three primary colours. It follows that 

 it is possible to construct an immeasurably greater number of 

 combinations here than with the few letters which build up our 

 words. Nor must we forget the extremely rapid changes of 

 which the images of sight are capable. No wonder, then, if our 

 senses speak to us in language which can express far more delicate 

 distinctions and richer varieties than can be conveyed by words. 



This is the solution of the riddle of how it is possible to see; 

 and, as far as I can judge, it is the only one of which the facts 

 at present known admit. Those striking and broad incongruities 

 between Sensations and Objects, both as to quality and to 

 localisation, on which we dwelt, are just the phenomena which 

 are most instructive ; because they compel us to take the right 

 road. And even those physiologists, who try to save frag- 

 ments of a pre-established harmony between sensations and 

 their objects, cannot but confess that the completion and refine- 

 ment of sensory perceptions depend so largely upon experience, 

 that it must be the latter which finally decides whenever they 

 contradict the supposed congenital arrangements of the organ. 

 Hence the utmost significance which may still be conceded to 

 any such anatomical arrangements is that they are possibly 

 capable of helping the first practice of our senses. 



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