Page:Popular Science Monthly Volume 81.djvu/69

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world which lose nothing in exactness but gain something altogether new—esthetic feeling.

Vision is the sense which provides the mind with an overwhelming preponderance of the sensations which lie at the basis of esthetic conceptions. If it can be demonstrated that esthetic visual ideas are founded upon reactions which are dependent upon anatomical peculiarities of the sense organ, the main purpose of this argument will have been accomplished. The evidence follows:

The globe of the eye is admittedly the analogue of a photographic camera, but it is marked by mechanical imperfections that would completely unfit it for the projection of a sharp image upon the sensitive plate. For the eye lets in light not only through the pupil, which corresponds with the aperture in the photographic diaphragm, but the sidewall of the globe—the sclerotic coat and its underlying choroid coat—are penetrable to the light. Consequently, the whole retina must be bathed in a dim light which has entered through the wall of the eyeball. This light is diffuse, and since it has traversed many blood streams it must have acquired a reddish color.[1]

Under ordinary conditions of vision then, there is thrown upon the center of the retina a more or less sharply defined image of objects the light from which has entered the pupil. In addition, the whole of the retina is illuminated by a diffuse reddish glow, due to light leaking through the white of the eye, a condition the parallel of which would completely subvert the efficiency of an artificial camera. Apparency, then, evolution has produced for us an optical instrument which is hopelessly defective. But the sensitive film of the eye is alive and the impressions formed on it are interpreted through the aid of living structures. It is conceivable that what seem to be mechanical deficiencies in the eye may be compensated or even turned into actual benefits through physiological agency.

It is a familiar law of chromatics that whenever an objective color falls upon the retina, the affected area becomes fatigued for that color and refreshed for its complementary. The complementary color of red is green. Under the conditions named, then, the irritability of the retina for green is continually maintained through the influence of light leaking through the sclerotic coat. So long as this side light penetrates the globe of the eye, and such is the habitual condition in daylight, the perception for green is automatically refreshed and this color, therefore, excels all its companions of the spectrum in its ability to play upon the sensorium without inducing fatigue.

Now the characteristic tint of vegetation is green. A tree clothed with verdure never wearies the color sense. But look at this same tree through an opaque mask having eye-holes admitting light only

  1. Cf. Brücke, Pogg. Annalen, Bd. LXXXIV., S. 418.