VETERINAEY OPHTHALMOLOGY. 21 



closed at the apex, which corresponds to the orbital 

 hiatus. In the ordinary position of the head the open- 

 ing of this cone is directed forward, downward and 

 outward. The bones which go to make the orbital 

 cavity are the frontal, sphenoid, superior maxillary, 

 malar, palate, ethmoid and lachrymal. The optic for- 

 amen, situated at the apex of the cone, transmits the 

 optic nerve and ophthalmic artery. The superior orbi- 

 tal fissure transmits the third, fourth and sixth nerves, 

 ophthalmic branch of the trigeminus and the superior 

 and interior ophthalmic veins. The inferior orbital 

 fissure gives passage to the malar and infra-orbital 

 nerves, and a facial branch of the ophthalmic vein. 

 (See Fig 41.) The supra-orbital notch, at the upper 

 and inner margin of the orbit, contains the supra- 

 orbital nerves and artery as they pass to the forehead. 

 In addition to the bulbus, muscles, vessels, etc., the 

 orbit contains much adipose tissue. 



There is a limiting membrane between the globe and 

 conjunctiva and the cellulo-fatty tissue, called Tenon's 

 capsule. To some extent it ensheaths the muscles, 

 nerves and vessels that pass through it, and is con- 

 tinuous with the periosteum of the orbit, as Avell as 

 with the conjunctiva. It is somewhat analogous to the 

 pleura, and serves as a cup in which the globe revolves. 

 It constitutes a secondary attachment for the ocular 

 muscles. The dura mater is firmly attached at the 

 sphenoidal fissure and optic foramen, and is continuous 



