THE HEAD, ANTERIOR. 49 



The Orbital Fascia, or Periosteum. 



This lines the interior of the bones composing the orbit, 

 is continuous with the dura through the optic foramen and 

 the sphenoidal fissure, forms the capsule of the lachrymal 

 gland, the lining for the lachrymal canal, and the pulley 

 for the superior oblique muscle, at the anterior margin of 

 the orbit becomes continuous with the periosteum covering 

 the exterior of the bones, and also sends to the eye-lids a 

 fibrous expansion the palpebral fascia. 



The Muscular Fasciae. 



This consists of the connective tissue envelopes for the 

 muscles and the eye-ball anterior to the insertion of the recti 

 and oblique muscles, from where it is reflected on to the eye- 

 lids and orbital margin. This layer also forms the cover- 

 ing for the nerves and vessels. 



Tenon's Capsule. 



This is the connective sheath for the optic nerve and the 

 posterior two-thirds of the eye-ball. Anteriorly it passes 

 into the fasciae for the muscles, the sclerotic coat, and ocular 

 conjunctiva of the eye ; posteriorly it blends with the orbital 

 fascia. 



The Frontal Nerve. Diag. 4. Fig. n. 



This enters the orbit just external to the fourth nerve, 

 crosses the levator palpebrse, and at the middle of the 

 orbit divides into the supra-orbital and supratrochlear 

 nerves. 



The former leaves the orbit through the supra-orbital 

 foramen or notch, and the latter, after passing above the 

 pulley of the superior oblique, leaves at the inner angle of 

 the orbit. For the termination distribution of these nerves 

 see page 25. 

 4 



