Page:Popular Science Monthly Volume 81.djvu/72

66 mechanism of ocular fixation must carry out its movements with an ease or effort determined by the external configuration brought into attention. It has been shown that in oblique movements of the eyes there is a definite rotatory movement of the globes, so that in following any line departing obliquely from the prime axis of vision it seems obvious that the fixation mechanism would suffer less fatigue when this line is curved objectively to correspond with the normal rotation round the visual axis. In following oblique lines which are objectively straight the fixation mechanism must be continually harrassedharassed [sic] by the voluntary effort to maintain the contemplated line in the horopter.

No homily is needed to convince the modern physician of the paramount psychological importance of the motor sensations arising from the coordinations of the external eye muscles. As sensory disasters from eyestrain often result in muscular unbalance, it is not difficult to believe, conversely, that peculiar advantages may spring from unobtrusive objective aids to the action of the intricate machinery of fixation whereby the eye is enabled to rove over a picture without conscious effort. According to this view, then, the curved lines of the Parthenon are psychologically straight to the onlooker in so far as they parallel the normal inclination of the after-image in oblique vision. It is easy to believe that the physiological result of such relations is rest, absence' of fatigue. But kind nature repays subconscious physiological coordination in a rich and peculiar way; the thing so seen and understood without effort arouses a new class of ideas—an esthetic feeling—beauty.

It may be objected to the foregoing argument that, though the outline of one side of a column may by reason of its curve allow the eye to glance along it without the effort of fixation, that of the opposite side, forming a reciprocal arc, must simultaneously offer an equally exaggerated impediment to ease of vision. I answer that the percipient mind tends to neglect all sensory impressions which interfere with the homogeneity of a mental picture. The infinite details of a landscape impressed upon the outskirts of the retina? give rise for the most part to mental double images, but these in no wise disturb the acuteness of vision for an object projected on the retinal foveæ. Moreover, it is not intended here to imply that the idea elaborated above contains the whole physiologic basis of the esthetic charm of the Parthenon. Indeed, the author of the admirable paper which has been quoted, whose thesis, by the way, ascribes the preeminence of Greek art to its foundation on physiological principles, himself gives other interpretations to the psychic impression produced by the temple. These explanations, however, do not displace, but rather complement that detailed above.

In the foregoing discussion evidence has been offered along two