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