r forms with his finger in the air. He
said he had no idea of those figures.

"_Third Experiment._--The windows of the room were darkened,
with the exception of one, toward which the patient, closing his
eye, turned his back. At the distance of three feet, and on a
level with the eye, a solid _cube_ and a _sphere_, each of four
inches diameter, were placed before him. I now let him open his
eye. After attentively examining these bodies, he said he saw a
_quadrangular_ and a _circular_ figure, and after some
consideration he pronounced the one a _square_ and the other a
_disk_. His eye being then closed, the cube was taken away, and
a disk of equal size substituted and placed next to the sphere.
On again opening his eye he observed no difference in these
objects, but regarded them both as disks. The solid cube was now
placed in a somewhat oblique position before the eye, and close
beside it a figure cut out of pasteboard, representing a plane
outline prospect of the cube when in this position. Both objects
he took to be something like flat quadrates. A pyramid, placed
before him with one of its sides toward his eye, he saw as a
plane triangle. This object was now turned a little, so as to
present two of its sides to view, but rather more of one side
than of the other; after considering and examining it for a long
time, he said that this was a very extraordinary figure; it was
neither a triangle, nor a quadrangle, nor a circle; he had no
idea of it, and could not describe it. 'In fact,' said he, 'I
must give it up.' On the conclusion of these experiments I asked
him to describe the sensations the objects had produced,
whereupon he said that immediately on opening his eye he had
discovered a difference in the two objects, the cube and the
sphere, placed before him, and perceived that they were not
drawings; but that he had not been able to form from them the
idea of a square and a disk, _until he perceived a sensation of
what he saw in the points of his fingers_, as if he really
touched the objects. When I gave the three bodies, the sphere,
cube, and pyramid, into his hand, he was much surprised that he
had not recognized them as such by sight, as he was well
acquainted with them by touch. These experiments prove the
correctness of the hypothesis I have advanced elsewhere on t