DISSECTION OF THE ORBIT 



335 



the posterior part of this muscle the small trochlear or fourth cerebral nerve 

 will be discovered. The dissector often fails to find this nerve, because as 

 a general rule he looks for it too far forwards. Lastly, the lacrimal nerve 

 and artery will be found, running along the lateral wall of the orbit, above 

 the level of the upper margin of the lateral rectus muscle. 



These structures must be thoroughly cleaned and isolated by the removal 

 of the fat from around them. As the superior oblique muscle ^ is 

 followed anteriorly it will be found to end in a slender tendon, which 

 passes through a ring-like pulley attached to the medial angular process of 



Lacrimal gland 



Frontal nerve 

 Short ciliary nerves -\r 



Infra-trochlear nerve 



-Supra-trochlear nerve 



- Supra-orbital nerve 



- Anterior ethmoidal nerve 

 -Long ciliary nerves 



Naso-ciliary nerve 



Ciliary ganglion 



Ophthalmic nerve 



jf -VOptic nerve 



Maxillary nerve 

 Motor root of trigeminal 

 Mandibular nerve 



Semilunar ganglion (thrown laterally) 



FIG. 133. The Ophthalmic Nerve of the Left Side. The semilunar ganglion 

 and the nerves have been everted and turned over to show the motor root. 



the frontal bone. This pulley must be defined, and the tendon of the 

 muscle followed laterally from it to its insertion into the eyeball. Note that 

 the levator palpebrse superioris lies upon the upper surface of the superior 

 rectus, and, if it is raised, a nerve twig will be noticed emerging from the 

 substance of the rectus superior for the supply of the levator palpebrce 

 muscle. This is a branch of the superior division of the third nerve. 



The dissection of the above parts will be facilitated by grasping the 

 anterior part of the eyeball with the forceps and drawing it forwards. It 

 may be retained in this position by running a fine needle and thread through 

 the ocular conjunctiva and stitching it to the nose. In doing this, however, 

 take care that the needle does not penetrate the cornea, because this might 

 render the subsequent inflation of the eyeball impossible. 



