INTRODUCTION. XXXV 



one eye is weaker than the other, we squint involun- 

 tarily, and it finally becomes a habit, in order to avoid 

 the confusion of perception from two unequal images 

 on the brain. This accounts for squinting, both in early 

 life, from some congenital cause, and for that squinting 

 which is the result of inflammation, in more advanced 

 life. A little reflection on this head will satisfy us; for 

 as a single judgment or perception is, for the most part, 

 formed from the two impressions, one on each eye, how 

 is it possible that this judgment can be accurate, when 

 the same body is presented at the same moment with 

 vivid or faint colours, accordingly as it was painted on 

 the strong or weak eye? 



The Ear is subjected to the same law as the eye. If, 

 in the two sensations composing the act of hearing, one 

 is received upon an organ better developed than the 

 other, and more discriminating in its functions, it will 

 leave an impression more clear and distinct; but the 

 brain being affected simultaneously by the unequal im- 

 pressions, will be the seat of an imperfect conception. 

 This case constitutes a false ear in music, and from the 

 impressions being continually confused, prevents the 

 individual from judging rightly between harmony and 

 dissonance. 



A similar reasoning has been founded by Bichat upon 

 the structure of the Nose, Mouth, and Organs of Touch. 

 He believes also that the brain itself, as the seat of the 

 mind, may become the cause of error in our ideas, when 

 the two halves of it are not perfectly alike; for example, 

 if one of the hemispheres be more strongly organized 

 than the other, better developed every where, and more 

 susceptible of a vivid impression. The brain transmits 

 to the soul the impression or impulse derived from the 

 senses, as the latter transmit to the brain their impres- 

 sions; it is, therefore, to be believed that the soul will 

 perceive confusedly, when the hemispheres, being une- 



