S. 46.

The facts here mentioned in no wise contradict a phenomenon recently
discussed by McDougall,[3] wherein eye-movements revive sensations
which had already faded. Thus an eye-movement will bring back an
after-image which was no longer visible. This return to vividness
takes place after the movement has been completed, and there is no
contention that the image is seen just during the movement.

[3] McDougall, W., _Mind_, N.S., X., 1901, p. 52.

The disappearance of after-images during eye-movements is mentioned by
Fick and Guerber,[4] who seek to explain the phenomenon by ascribing it
to a momentary period of recovery which the retina perhaps undergoes,
and which would for the moment prevent further stimulations from being
transmitted to the optic nerve. Exner observes that this explanation
would not, however, apply to the disappearance of the vessel-figure,
the circulation phenomenon, the foveal figure, the polarization-sheaf
of Haidinger, Maxwell's spot, or the ring of Loewe; for these phenomena
disappear in a similar manner during movement. Exner offers another
and a highly suggestive explanation. He says of the phenomenon (_op.
citat._, S. 47), "This is obviously related to the following fact,
that objective and subjective impressions are not to be distinguished
as such, so long as the eye is at rest, but that they are immediately
distinguished if an eye-movement is executed; for then the subjective
phenomena move with the eye, whereas the objective phenomena are not
displaced.... This neglect of the subjective phenomena is effected,
however, not by means of an act of will, but rather by some central
mechanism which, perhaps in the manner of a reflex inhibition,
withholds the stimulation in question from consciousness, without our
assistance and indeed without our knowledge." The suggestion of a
central mechanism which brings about a reflex inhibition is the
significant point.

[4] Fick, Eug., and Guerber, A., _Berichte d. ophthalmologischen
Gesellschaft in Heidelberg_, 1889.

It is furthermore worth noting that movements of the eyelid and
changes in the accommodation also cause the after-images to disappear
(Fick and Guerber), whereas artificial displacement of the eye, as by
means of pressure from the finger, does not interfere with the images
(Exner).

Another motive for suspecting anaesthesia during eye-movement is found
by Dodge,[5] in the fact that, "One may watch one's eyes as closely as