74 ON THE KELATION OF OPTICS TO PAINTING. 



myself to a traveller who has entered upon them by 

 a steep and stony mountain path, but who, in doing 

 so, has passed many a stage from which a good point 

 of view is obtained. If therefore I relate to you what 

 I consider I have observed, it is with the understand- 

 ing that I wish to regard myself as open to instruction 

 by those more experienced than myself. 



The physiological study of the manner in which 

 the perceptions of our senses originate, how impressions 

 from without pass into our nerves, and how the condi- 

 tion of the latter is thereby altered, presents many 

 points of contact with the theory of the fine arts. On 

 a former occasion T endeavoured to establish such a 

 relation between the physiology of the sense of hearing, 

 and the theory of music. Those relations in that case 

 are particularly clear and distinct, because the elemen- 

 tary forms of music depend more closely on the nature 

 and on the peculiarities of our perceptions than is the 

 case in other arts, in which the nature of the material 

 to be used and of the objects to be represented has 

 a far greater influence. Yet even in those other 

 branches of art, the especial mode of perception of 

 that organ of sense by which the impression is taken 

 up is not without importance ; and a theoretical in- 

 sight into its action, and into the principle of its 

 methods, cannot be complete if this physiological ele- 

 ment is not taken into account. Next to music this 



