PLATES.

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Charts of the Sciences, at end of volume.

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Studies in perception.

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EYE-MOVEMENT AND CENTRAL ANAESTHESIA.

By Edwin B. Holt.

I. THE PROBLEM OF ANAESTHESIA DURING EYE-MOVEMENT.

A first suggestion of the possible presence of anaesthesia during eye-movement is given by a very simple observation.  All near objects seen from a fairly rapidly moving car appear fused.  No further suggestion of their various contour is distinguishable than blurred streaks of color arranged parallel, in a hazy stream which flows rapidly past toward the rear of the train.  Whereas if the eye is kept constantly moving from object to object scarcely a suggestion of this blurred appearance can be detected.  The phenomenon is striking, since, if the eye moves in the same direction as the train, it is certain that the images on the retina succeed one another even more rapidly than when the eye is at rest.  A supposition which occurs to one at once as a possible explanation is that perchance during eye-movement the retinal stimulations do not affect consciousness.

On the other hand, if one fixates a fly which happens to be crawling across the window-pane and follows its movements continuously, the objects outside swim past as confusedly as ever, and the image of the fly remains always distinct.  Here the eye is moving, and it may be rapidly, yet both the fly and the blurred landscape testify to a thorough awareness of the retinal stimulations.  There seems to be no anaesthesia here.  It may be, however, that the eye-movement which follows a moving object is different from that which strikes out independently across the visual field; and while in the former case there is no anaesthesia, perhaps in the latter case there is anaesthesia.