DISSECTION OF THE ORBIT 



345 



superior orbital fissure. The rectus lateralis is distinguished 

 from the^.others by arising from a fibrous arch, the extremities 

 of which are termed its two heads of origin. The lower 

 head arises in common with the rectus inferior from the 

 body of the sphenoid, where this bounds the medial end of 

 the superior orbital fissure ; the upper head is attached above 

 the superior orbital fissure upon the lateral side of the optic 

 foramen, where its origin becomes continuous with the 

 superior rectus. Through the archway which intervenes 

 between the two heads of the lateral rectus pass the two 



Frontal nerve 



Lacrimal nerve 



\ 



superior rectus 



Levator palpebrae 

 superioris 



Superior division of 

 third nerve 



Fourth nerve 



Superior oblique 



Optic foramen 



r Medial rectus 



Inferior rectus 



Inferior division of 

 third nerve 



Lateral rectus 



Sixth nerve 

 Inferior orbital fissu 



FIG. 137. Diagram of the Orbital Cavity, and of the origin of the ocular 

 muscles in relation to the optic foramen and the superior orbital fissure, 

 and the nerves that traverse the latter. 



divisions of the oculo-motor nerve, the naso ciliary nerve, the 

 abducent nerve, and the ophthalmic veins (Fig. 137). 



A better view of these attachments may be obtained by dividing the 

 optic nerve close to the optic foramen and turning the eyeball anteriorly. 



The manner in which the recti muscles are inserted into 

 the eyeball should next be studied. Each ends in a delicate 

 membranous tendon, which is inserted into the sclera, about 

 a quarter of an inch posterior to the sclero-corneal junction. 



Nervus Oculomotorius. The two divisions of this nerve 

 enter the orbit through the superior orbital fissure, between 

 the two heads of the lateral rectus. The superior division has 



