245 



ing during the first months of the life of the foetus; cataract, ait affec- 

 tion which consists in the opacity of the crystalline lens or its capsule ; 

 the glaucoma, or defect of transparency in the vitreous humour, weak- 

 en or altogether destroy sight, by impeding the passage of the rays to 

 the retina. This membrane itself must be of tempered sensibility to be 

 suitably affected by their contact. The choroid, the concavity of which 

 it fills, must present a coating black enough to absorb the rays that pass 

 through it. It is to the sensible decay of the dye of the choroid in ad- 

 vancing years, as much as to the collapsing induration, and discolouring 

 of different parts of the eye, and the impaired sensibility of the retina 

 from long use, that we ascribe the confusion and weakness of sight in 

 old people. The extreme delicacy of the eyes of the Minos pro vesequally 

 the necessity of the absorption of light, by the black coating which cover 

 the choroid. 



The eyes are, of all the organs of sense, those which are the most deve- 

 loped in a new-born child. They have then nearly the bulk which they 

 j*re Ur retain during life. Hence it happens, that the countenance of chil- 

 dren^whose eyes are proportionably larger, is seldom disagreeable, be- 

 cause it is chiefly in these organs that physiognomy seeks expression. 

 Might we not say, that if Nature sooner completes the organ of sight, it 

 is because the changes which it produces on the rays of light, arising 

 purely from a physical necessity, the perfection of the instrument was 

 required for the exercise of the sense ? 



The eyes are not immoveable in the place they occupy. Drawn into 

 very various motions, by four recti muscles, and two oblique, they direct 

 themselves towards all objects of which we wish to take cognizance; and 

 it is observed, that there is, between the muscles which move the two eyes, 

 such, a correspondence of action, that these organs turn^at once the same 

 way, and are directed, at once, towards the same object, in such a manner, 

 that the visual axes are exactly parallel. It sometimes happens, that this 

 harmony of motion is disturbed ; and hence squinting; an affection 

 which depending almost always, on the unequal force of the muscles of the 

 eye, may be distinguished into as many species as there are muscles which 

 can draw the globe of the eye into their direction, when from any cause, 

 they become possessed of a predominating power. Buffon has further as- 

 signed as a cause of squinting, the different aptitude of the eyes to be affect- 

 ed by light. According to this celebrated naturalist, it may happen, that 

 one of the eyes being originally of greater sensibility, the child will close 

 the weaker to use the stronger, which is yet strengthened by exercise, 

 whilst repose still weakens the one which remains in inaction. The exami- 

 nation of a great many young people, who had fullen under military con- 

 scription, and claimed exemption, on the score of infirmities, has shown me 

 that squinting is constantly connected with the unequal power of the eyes. 

 Constantly, the inactive eye is the weakest, almost useless, and it was quite 

 a matter of necessity that the diverging globe should be thus neutralized, 

 else the image it would have sent to the brain, different from that which the 

 sound eye gives, would have introduced confusion into the vital functions. 

 The squinting eye, being inactive, falls by degrees into that state of debi- 

 lity, from default of exercise, which Brown has so well called indirect de- 

 bility. 



The sense of sight appears to me, much rather to deserve the name which 

 J. J. Rousseau has given to that of smell, of sense of the imagination. 

 Like that brilliant faculty of the soul, the sight, which furnishes us with 



