144 



THE OCULAR MUSCLES. 



[BOOK in. 



inserted in positions corresponding to their several names into the 

 sclerotic, behind the cornea, the bundles of fibres of the tendons 

 being interwoven with those of the sclerotic. The tendon of 

 the internal rectus on the median or nasal side of the eyeball 

 is the broadest of the four; that of the superior rectus on the 

 upper surface being somewhat narrower, and those of the inferior 

 rectus on the under surface and of the external rectus on the 

 lateral or temporal side, still narrower (Fig. 155). The inser- 

 tion of the superior rectus lies nearer to that of the external 

 rectus than to that of the internal rectus ; its position therefore 

 is not exactly median, indeed for two-thirds of its width it lies 

 in the upper lateral quadrant of the sclerotic ring. The inser- 

 tions of the external and of the internal rectus are both median. 

 The insertion of the internal rectus is the one closest to, and 

 that of the superior rectus the one farthest away from the cornea, 

 and the latter slants so as to be nearer the cornea at its median 

 than at its lateral end. 



LEFT EYE 



FROM TEMPORAL SIDE 

 Sup.R 



V SU P Ext. 



Inf.O 



Ext.R 



Inf.O 



FIG. 155. THE LEFT EYE SEEN FROM A, THE TEMPORAL SIDE. B, FROM 



ABOVE, SHEWING THE INSERTIONS OF THE OCULAR MUSCLES. (JeSSOp.) 



The superior oblique muscle, or trochlear or pathetic muscle, 

 taking origin from the back of the orbit near the origin of the 

 straight muscles and running forward internal to the superior 

 rectus, ends in a tendon, which changing its direction by means of 

 a pulley (trochlea), and passing beneath the superior rectus is in- 

 serted into the sclerotic in the upper region of the bulb towards 

 its hind part. The line of insertion of the tendon (Fig. 155) runs 

 obliquely from the temporal towards the nasal side, its mid-point 

 lying not far from the vertical meridian of the eyeball. 



The inferior oblique muscle arises from the front of the floor 

 of the orbit on the nasal side ; it is directed at first backwards 

 to the temporal side, underneath the inferior rectus, between that 

 and the floor of the orbit, and then passing upwards and back- 



