Harvard Psychological Studies, Volume 1 | Page 4

[4] Fick, Eug., and Gürber, 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 Gürber), 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 anæsthesia during eye-movement is
found by Dodge,[5] in the fact that, "One may watch one's eyes as
closely as possible, even with the aid of a concave reflector, whether
one looks from one eye to the other, or from some more distant object
to one's own eyes, the eyes may be seen now in one position and now
in another, but never in motion." This phenomenon was described by
Graefe,[6] who believed it was to be explained in the same way as the
illusion which one experiences in a railway coach when another train is
moving parallel with the coach in which one sits, in the same direction
and at the same speed. The second train, of course, appears motionless.
[5] Dodge, Raymond, PSYCHOLOGICAL REVIEW, 1900, VII., p.
456.
[6] Graefe, A., Archiv f. Ophthalmologie, 1895, XLI., 3, S. 136.

This explanation of Graefe is not to be admitted, however, since in the
case of eye-movement there are muscular sensations of one's own
activity, which are not present when one merely sits in a coach. These
sensations of eye-movement are in all cases so intimately connected
with our perception of the movement of objects, that they may not be in
this case simply neglected. The case of the eye trying to watch its own
movement in a mirror is more nearly comparable with the case in
which the eye follows the movement of some independent object, as a
race-horse or a shooting-star. In both cases the image remains on
virtually the same point of the retina, and in both cases muscular
sensations afford the knowledge that the eye is moving. The
shooting-star, however, is perceived to move, and the question remains,
why is not the eye in the mirror also seen to move?
F. Ostwald[7] refutes the explanation of Graefe from quite different
considerations, and gives one of his own, which depends on the
geometrical relations subsisting between the axes of vision of the real
eye and its reflected image. His explanation is too long to be here
considered, an undertaking which indeed the following circumstance
renders unnecessary. While it is true that the eye cannot observe the full
sweep of its own movement, yet nothing is easier than to observe its
movement through the very last part of the arc. If one eye is closed, and
the other is brought to within about six inches of an ordinary mirror,
and made to describe little movements from some adjacent part of the
mirror to its own reflected image, this image can almost without
exception be observed as just coming to rest. That is, the very last part
of the movement can be seen. The explanation of Ostwald can
therefore not be correct, for according to it not alone some parts of the
movement, but absolutely all parts alike must remain invisible. It still
remains, therefore, to ask why the greater part of the movement eludes
observation. The correct explanation will account not only for the
impossibility of seeing the first part of the movement but also for the
possibility of seeing the remainder.
[7] Ostwald, F., Revue Scientifique, 1896, 4e Série, V., p. 466.
Apart from the experience of the eye watching itself in a glass, Dodge

(loc. citat.) found another fact which strongly suggested anæsthesia. In
the course of some experiments on reading, conducted by Erdmann and
Dodge, the question came up, how "to explain the meaning of those
strangely rhythmic pauses of the eye in reading every page of printed
matter." It was demonstrated (ibid., p. 457) "that the rhythmic pauses in
reading are the moments of significant stimulation.... If a simple letter
or figure is placed between two fixation-points so as to be
irrecognizable from both, no eye-movement is found to make it clear,
which does not show a full stop between them."
With these facts in view Dodge made an experiment to test the
hypothesis of anæsthesia. He proceeded as follows (ibid., p. 458): "A
disc of black cardboard thirteen inches in diameter, in which a circle of
one-eighth inch round holes, one half inch apart, had been punched
close to the periphery all around, was made to revolve at such a
velocity that, while the light from the holes fused to a bright circle
when the eye was at rest, when the eye moved in the direction of the
disc's rotation from one fixation point, seen through the fused circle of
light, to another one