WITH PHYSIOLOGICAL OBSERVATIONS. 65 



correctly described by him. When he was asked to point out either of the figures, 

 he never moved his hand directly and decidedly, but always as if feeling, and with 

 the greatest caution ; he pointed them out, however, correctly. A line consisting of 

 angles, or in other words, a zigzag, and a spiral line, both drawn on a sheet of paper, 

 he observed to be different, but could not describe them otherwise than by imitating 

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



3rd Experiment. The windows of the room were darkened, with the exception of 

 one, towards 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. Allowing him to move the head in a lateral di- 

 rection no further than was necessary to compensate the point of view of the right 

 amaurotic eye, I now let him open his eye, and requested him to state decidedly what 

 he observed. 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 disc. His eye being then closed, the cube was taken away, and a 

 disc 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 discs. 

 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 v/hen in this position. Both objects he took to be something like flat 

 quadrates. A pyramid, placed before him with one of its sides towards his eye, he 

 saw as a plain 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 ex- 

 periments, I asked him to describe the sensations the objects had produced, where- 

 upon 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 disc, 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 these solid mathematical 

 figures by his touch. These experiments prove the correctness of the hypothesis I 

 have advanced elsewhere on the well-known question put by Mr. Molyneux to Locke, 

 which was answered by both these gentlemen in the negative, and has been much 

 discussed since their time. 



4th Experiment. In a vessel, containing water to about the depth of one foot, was 

 placed a musket-ball, and on the surface of the water a piece of pasteboard, of the 

 same form, size, and colour as the ball. The patient could perceive no difference in 

 the position of these bodies ; he believed both to be upon the surface of the water. 



MDCCCXLI. ic 



