28 RESPECTIVE ACTION OF THE RETINA AND MIND. 



Action of the retina and of the sensorium in vision.* 



Under this head may be mentioned some of the highly interesting 

 particulars of a case in which a well-informed youth, blind from birth, 

 had the sight of one eye restored by a successful operation performed 

 by Dr. Franz. \ The patient had congenital cataract of both eyes, with 

 internal strabismus to such a degree, that nearly one half of each 

 cornea was hidden by the inner canthus. The right eyeball had atro- 

 phied in early life, in consequence of inflammation ensuing after the 

 operation of keratonyxis, and became completely amaurotic. The left 

 retained sensibility to the impression of light, but had no power for the 

 perception of objects. At the age of seventeen the operation for cataract 

 was successfully performed on the left eye, and the sensitiveness of the 

 retina was at once made evident by the blaze of light perceived when the 

 eye was opened. On the third day after the operation, the eye was again 

 opened, when the patient perceived an extensive field of light in which no 

 object could be distinguished : everything appearing dull, confused, and in 

 motion. During the next few days, at the times of the eye being open, 

 nothing was seen except a number of " opaque watery spheres, which 

 moved with the movements of the eye, but, when the eye was at rest, re- 

 mained stationary, and then partially covered each other." The spheres 

 gradually became more transparent, and the patient was enabled to per- 

 ceive, through them, as it were, a slight difference in surrounding objects : 

 but, owing to the pain produced by the light, the eye could not be kept 

 open long enough to allow of a distinct visual impression of any object 

 being perceived. The appearance of spheres had entirely vanished at the 

 end of two weeks. When the intolerance of light had so far abated that 

 the patient could, without pain, regard an object for a sufficient time to 

 gain a clear idea of it, he was able to perceive and correctly describe 

 vertical and horizontal lines, triangles, spirals, and other black figures 

 drawn on paper and placed before him. His perception and discrimi- 

 nation of different colours placed on a black ground were equally cor- 

 rect. An answer to the well-known question put by Mr. Molyneux 

 to Locke | was next experimentally sought. A solid cube and a sphere, 

 each of four inches diameter, were placed before the patient at the dis- 

 tance of three feet, and on a level with the 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 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, 



* Miiller's Physiology, p. 1162. t Philosophical Transactions, 1841, pp. 5968. 



$ Muller's Physiology, p. 1176. 



