Chap. 41.] Caufe of Squinting. 399 



ject, though the mufcles fo far act in concert with eacfr 

 other, as to move both eyes the fame way at the fame 

 inftant of time. Dr. Jurin obferves, that this vicious 

 habit may eafily be contracted by a child, if he is 

 laid in his cradle in fuch a pofition as to perceive the 

 light with one eye only. 



The moft common caufe of fquinting is, however, 

 an inferiority in the fight of one of the eyes. Dr. 

 Reid aflferts, that having examined above twenty per- 

 fons, who fquinted, he found in all of them a defect 

 in the fight of one eye. Four of them only had fo 

 much of diftinct vifion in the weak eye as to be able 

 to read with it, while the other was covered j the reft 

 faw nothing diftinctJy with the defective eye *. 



When the eyes are equally good, we fee witfv both 

 eyes more diftinctly than with one, by about a thirteenth 

 part ; but when the eyes are unequal in their powers, 

 objects appear lefs diftinct with both eyes than with 

 one. It is no wonder, therefore, that fuch perfons 

 mould chufe to make ufe of one eye only, and to 

 turn the other afide ; the weak eye, in this cafe, is 

 generally turned to the nofe, becaufe in that fituation 

 the direction of its axis is as diftant as poffible from 

 that of the good eye j and befides. this, the nofe cot>- 

 ceals many objects from its view. 



This is, however, not the only caufe of fquinting ; 

 it is fometimes, though rarely, the effect of habit, as 

 was intimated refpecting children being laid in the 

 cradle with one eye turned from the light, or covered. 

 When the eye that fquints is turned outwards towards 

 the temples, that cad of the eye is commpnlv the mere 

 effect of habit. 



If the eyes differ much in point of goodnefs, the 

 cure will be extremely difficult. When they do not 

 j* Reid';. Inquiry into Human Mind, p. 2^3. 



materially 



