IMAGES NOT FORMED ON THE RETINA. 343 



tion of luminous influence, enabling the animal to distinguish 

 light from darkness, not only in the general way of a blind 

 man conscious of a change of temperature in passing from 

 sunlight into shade, but also in the special way of minute 

 local variations, such as are caused by the shadows of near 

 objects. 



I remember once being seated with a philosophic friend, 

 and much bored by the presence of a morning caller — a large 

 white-waistcoated man, " such an ass, and so respectable ! " 

 stiff with ignorance and haughtiness : the kind of man who 

 seems afraid of lowering his eyebrow lest it should crease his 

 cravat. He droned away about " the house " and Lady 

 Jane, about his tenants, and what he had said on several 

 occasions, till my patience was exliaiisted ; and thinking 

 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-waistcoat preciiHtately retreated. 

 He would not wait to hear the development of that mad pro- 

 position ; yet, had he waited, he might have learned that the 

 eye is a tactile organ, and that what we call 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, transmitted 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 



