THE PHYSIOLOGICAL BASIS OF ESTHETICS 67 



different lines that structural or functional properties of the eye which, 

 considered from the purely physical point of view, would seem to im- 

 pair the efficiency of the organ as a registrar and transmitter of ob- 

 jective visual facts, not only do not confuse the recipient sensory nerve 

 centers, but, on the contrary, the psychical apprehension of objective 

 phenomena is distinctly modified by the reaction to such instrumental 

 defects in a manner which leads to the generation in consciousness of 

 a state or an atmosphere of feeling — esthetic feeling. It is as if the 

 stone rejected of the builders were made the chief of the corner. 



In pursuance of this line of thought I will offer one additional illus- 

 tration of the direct dependence of psychic perception upon what may 

 be termed the structural aberration of the visual apparatus. 



When external objects are viewed with one eye, held at rest, the 

 image upon the retina is exactly similar to that upon the sensitive 

 plate of the camera, it has length and breadth, but no depth, and it has 

 no power of directly arousing in the mind a perception of the third 

 dimension — projection. 



It is inconceivable, indeed, that an anatomical apparatus should be 

 capable of directly presenting to its sensory center an impression of 

 depth. Such a perception is of purely psychological construction from 

 simpler data derived from retinal impulses. By an exceedingly familiar 

 line of evidence it can be shown that the direct visual perception of 

 depth is dependent upon idiosyncrasies of binocular vision. It is a 

 physiological law that an object viewed by the two eyes appears to be 

 single only when the images Avhich it casts upon the retinas fall upon 

 " corresponding points " of the two surfaces. It is obviously of para- 

 mount importance to the instrumental efficiency of the eyes that there 

 should be a horopter in which objective and subjective facts must coin- 

 cide. It is well known that the fixation of objects by means of which 

 their images are retained upon corresponding retinal areas invokes ac- 

 tivity of most complex nerve-muscle machinery. Now when a small 

 solid object is viewed with both eyes, it is clear that the right eye must 

 see more of the right side of the object and the left eye more of the left 

 side. Therefore it is certain that the images on the two retinas can not 

 be identical and therefore can not exactly " correspond." 



Some extra-mundane theorists summing up these facts would nat- 

 urally reach the conclusion that distinct binocular vision is in its na- 

 ture impossible. Nevertheless we know that the mental picture of 

 external objects loses nothing essential in focal sharpness through 

 binocular vision but, on the other hand, the two unlike retinal pictures 

 combine, as it were, in the mind to form a new idea — the concept of 

 depth. 



Of all esthetic perceptions that of projection is the highest, the most 

 purely psychic. Through it the universe is instantly converted from a 



