ctor, 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, 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.
 Dodge, Raymond, PSYCHOLOGICAL REVIEW, 1900, VII., p. 456.
 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 simpl