176 British War Dogs 



To quote Mr. Romanes again : "No less constant must 

 be the work of mental inference, in compensating for the 

 effects of the ' blind spot ' upon the retina. For if the 

 vision be directed to a coloured surface, the part of the 

 surface, which, on account of the blind spot, is not really 

 seen, yet appears to be seen ; and not only so, but it 

 appears to be coloured the same tint as the rest of the 

 surface, whatever this may happen to be. Unconscious 

 inference supplies the colour. 



" The first or early stage of inference then is, that in 

 which inference arises in or together with perception, as when 

 we infer that a gnat is a bird, or that the portion of a sur- 

 face, corresponding to the blind spot of the retina, is 

 coloured like the surrounding portions of the surface. 

 Inference may here be said to be a constituent part of per- 

 ception. That this is the true explanation of the matter 

 is rendered evident, not only from the deductive con- 

 sideration first stated, but also from the inductive verifica- 

 tion, which is received from the facts, which arise, when 

 a man, who has been born blind, has been suddenly made 

 to see. A good case of this kind is the celebrated one of 

 the youth, (twelve years of age), whom Mr. Cheselden 

 couched for removing congenital cataracts from both eyes." 



Mr. Cheselden shows that although the boy saw, his 

 judgment as to the things that " touched his eyes " (as he 

 expressed it) was entirely guided by his sense of touch. 

 Continuing, he says " he thought no objects so agreeable as 

 those which were smooth and regular, though he could form 

 no judgment of their shape, or guess what it was in any 

 object that was pleasing to him. He knew not the shape of 

 anything, nor any one thing from another, however different 

 in shape or in magnitude ; but on being told what things 

 were, whose form he before knew from feeling, he would 



