IMAGES NOT FORMED ON THE RETINA. 361 



tenants, and what lie had said on several occasions, till 

 my patience was exhausted ; and thinldng nothing 

 more likely to hasten his departure than a touch of 

 Transcendental Anatomy, I turned to my friend, and, 

 as if resuming the thread of our conversation, remarked, 

 " Yes, it is singular to think of the eye being nothing 

 more than a tactile organ." Whereupon White-waist- 

 coat precipitately retreated. He would not wait to 

 hear the development of that mad proposition ; yet, 

 had he waited, he might have learned that the eye is 

 a tactile organ, and that what we caU vision is a com- 

 bination of the sensations of touch, and of temperature 

 of a specific kind. 



The common notion is, that objects are reflected as 

 images on the retina, and thence, as images, trans- 

 mitted to the brain. But nous avons change tout cela. 

 I have serious doubts whether an " image " is formed 

 on the retina at all ; and the strongest conviction that 

 no image is transmitted to the brain ; on the con- 

 trary, the thing transmitted is a sensation^ or group of 

 sensations, excited by what is caUed the "image." 

 The wave of light is translated into a nerve-stimulus, 

 the impression excites a sensation ; but the sensation 

 is due to the specific centre, not to the sj)ecific stimu- 

 lus of light ; as we know by the fact that any other 

 stimulus, such as pressure or electricity, is translated 

 into a precisely similar sensation. So that even if we 

 suppose an image to be formed on the retina, as it is 

 formed in a camera-obscura, it will not be transmitted 

 to the brain, but it will excite the specific sensations of 



