420 



MUSCLES OF THE EYE. 



more is necessary than to close the upper lid not forcibly, 

 however ; next to make pressure upon its upper part with a 

 pencil, bodkin, knitting-needle, or other hard body of small 

 diameter; and then, taking hold of the eyelashes, to draw 

 the lower edge of the lid forwards and upwards. By a dex- 

 terous movement of this kind, the lid may be everted without 

 any pain, a little temporary discomfort being all that the dis- 

 placement occasions ; its lining membrane is then exposed, 

 and any offending particle may be readily removed. 



538. The globe of the eye is moved by six muscles, which 

 are lodged within the bony cavity or orbit, hollowed-out in the 

 skull. All these muscles, except one, originate at the back of 



the orbit, and are inserted 

 into the sclerotic coat, near its 

 front, by broad thin tendons. 

 Four of them are termed recti 

 or straight muscles. One of 

 these, the superior rectus(e, fig. 

 209), is inserted at the upper 

 part of the eye, and conse- 

 quently by its contraction rolls 

 the globe upwards; another, 

 d, the inferior rectus, pro- 

 duces a corresponding move- 

 ment downwards. A third, the 



internal rectm ( which could 



nerve; d, inferior rectus muscle; e, supe- not be shown in this figure), 



rior rectus ;/, cut extremity of the ex- 11 fi o-ln"hp inwarrlc m- 



ternal rectus; g, end of the inferior * inwards, C 



obU^ue ; h, superior oblique ; i, elevator towards the nOS6 I whilst a 



of the upper lid ; A, lachrymal gland. /> ,1 ji /,i 



fourth, the external rectus (the 



cut extremity of which is seen at/), turns it outwards. Besides 

 these, there is a remarkable muscle, h, the superior oblique, 

 which originates at the back of the orbit, comes forwards to 

 the front, where its tendon passes through a pulley, and then 

 turns backwards to be inserted into the sclerotic coat, at a point 

 considerably behind the pulley. The sixth muscle, g, termed 

 the inferior oblique, does not arise, like the rest, from the 

 back of the orbit, but from its lower border. The action of 

 the two oblique muscles (which act in antagonism the one to 

 the other) appears to be to rotate the eyeball upon its axis ; 

 as is done when the eyes are kept steadily fixed upon any 



Fig. 209. VERTICAL SECTION OF THE 



