6 ACCOUNT OF A BOY 



serving, accordingly, the first visual perceptions even of a pa- 

 tient born deaf as well as blind, some very nice attentions 

 would be necessary for ascertaining the truth. But what pro- 

 portion do these bear to the numerous and refined precautions 

 which become indispensable, where the patient is reminded by 

 every query which is addressed to his ear, of the distance and 

 relative position of the questioner ? Justly might Diderot 

 say, — " Prepare?' et interroger un aveugle nS, ?i y eut point H6 

 une occupation indigne des talens reunis de Newton, Des- 

 cartes, Locke, et Leibnitz." — I mention this, because, 

 from the great degree of perfection to which this branch of 

 surgery has been lately carried, the increasing number of such 

 cases may be expected to multiply daily the opportunities of 

 philosophical experiment ; and it is of importance, that those 

 who may have the good fortune to enjoy them, should be ful- 

 ly apprized of the delicacy and the complexity of the pheno- 

 mena which they have to observe and to record *. 



In giving way to these speculations, I had proceeded on the 

 supposition, that the blindness of the patient was complete ; 

 not sufficiently attending to (what was long ago remarked by 

 Cheselden) the qualified sense in which the word blindness is 

 understood by surgical operators. " Though this gentleman 

 was blind" (says Cheselden, speaking of the patient whose 

 case he has so well described), " as is said of all persons zvho 

 " have ripe cataracts, yet they- are never so blind, from that 



cause, 



lid obstacle, by the action or pulse of the air upon his face. The same thing h 

 recorded of Dr Sanderson by his successor Mr Colson. 



* For the assistance of those to whom such a subject of observation may oc- 

 cur, some judicious hints are suggested in the Lettre sur les Aveugles a Fusage de 

 ceux qui voienU 



