12 ACCOUNT OF A BOY 



Tlie strong impression wliich Mr Wake's paper has lately 

 made on the public mind, and the support which it is probable 

 many readers will imagine that the argument against Chesel- 

 DEN derives from the observations of Mr Wardrop, will ac- 

 count sufficiently for the length to which the foregoing remarks 

 have extended : Or, if any farther apology be necessary, I trust 



that 



which he saw touched his eyes, he certainlj- coiikl not mean that they pressed 

 upon or resisted his eyes ; for the objects of sight never act upon the organ in 

 any way that resembles pressure or resistance. He could mean no more than 

 that they were close upon his eyes, or, to speak more properlj/, perhaps, that they 

 were in his eyes f."" Mr Smith's idea in this last clause, was, I presume, that the 

 local situation of the object was referred by the patient to the retina, where the 

 image of the object is painted. Now, I confess, for my own part, that although 

 I perfectly agree with Mr Smith in his criticism on Cheselden, I am by no 

 means satisfied, that the emendation which he has suggested of the young gen- 

 tleman's description is unexceptionable ; for it does not appear to me, that the 

 impression of a moderate light on the retina, is accompanied with any perception 

 of the part of tiie body on which the impression is made. Where the light, in- 

 deed, is so powerful as to produce pain, the case comes to be different ; for a sen- 

 sation of touch is then united with the proper sensations of sight ; and it is cha- 

 racteristical of all sensations of touch, that they are accompanied with a percep- 

 tion of the local situation of their exciting causes. This, however, it is well 

 known, does not take place with respect to the sensations of smell and of sound ; 

 nor do I imagine it to take place, prior to experience, with respect to the sen- 

 sations received by the eye. And, therefore, if a patient, in such circumstances, 

 should be led, by his first visual perceptions, to connect them locally with the or- 

 gan by which tliey are received, I should be inclined rather to ascribe this to 

 concomitant feelings of pain, (produced by the recent operation, or by the too 

 sudden impression of a strong light), than to any of those sensations which are 

 exclusively appropriated to the sense of sight. But this discussion it is un- 

 necessary for me to prosecute at present, as the opinion we may happen to form 

 with respect to it, (whatever that opinion may be), can never affect the truth of 

 that clause in Cheselden's statement, in which he asserts, upon the eoidence of 

 his own observations, that " when his patient first saw, he was unable to form any 

 judgment about distances." The remainder of the sentence is only a loose and 

 unintelligible comment of the young man on this simple fact. 



f See in Essay on tlie External Senses, by Adam Smith, LL. D. (published among his posthumous 

 papers.) 



