THE HEAD AND NECK. 147 



fissure and expands behind the sphenoidal fissure to form the cavernous sinus. 

 Its branches are : 



1. Lachrymal, with the external rectus, sixth nerve to lachrymal gland. 



2. Supraorbital, with the frontal nerve, levator palpebrae, superior rectus. 



3. Arteria centralis retinas, in centre of optic nerve to the retina. 



4. Anterior ethmoidal, with the nasal nerve to ethmoid cells. 



5. Posterior ethmoidal, to the posterior ethmoid cells. 



6. Palpebral arteries, to the upper and lower lids. 



7. Frontal artery, to the inner angle of the eye. 



8. Nasal artery, to the lachrymal sac and caruncula. 



9. Muscular branches, to the muscles of the eye. 

 10. Ciliary arteries, to the iris and choroid coat. 

 Hew would you classify the nerves? 



1 . Special sense : The optic nerve special of vision. 



( Motor : Third, to all except two muscles. 



2. < Motor : Fourth, to the superior oblique muscle. 



( Motor : Sixth, to the external rectus muscle. 



T Sensory : Nasal branch of ophthalmic, to the nose and orbit. 



3. < Sensory : Lachrymal branch of ophthalmic, to lachrymal gland. 



( Sensory : Frontal branch of ophthalmic, to forehead. 



4. Sympathetic, from cavernous plexus, to the ciliary ganglion. 



SUPERIOR LACHRYMAL GLAND 

 INFERIOR LACHRYMAL GLAND 



DUCT FROM SUPERIOR 6LAND 



UPPER EYELID PARTIALLY 

 DIVESTED OF SKIN 



UPPER PUNCTUM 



LACHRYMAL SAC, NEAR ITS FUNDt'S 



COMMON DUCT FORMED BY JUNC- 

 TION OF CANALICULI 



UPPER AND LOWER CANALICULI 

 LOWER PUNCTUM 



FIG. 104. LACHRYMAL APPARATUS. (After Schwalbe. ) 



The lachrymal gland you will find under the external angular process of 

 the frontal bone in the lachrymal fossa. (Fig. 103.) It has an orbital and a 

 palpebral part, a capsule, an artery, and a nerve. 



Define the periorbita and give its functions. 



This is the orbital periosteum. It forms the tarsal ligaments and the limbs of 

 the inner palpebral ligament, lines the floor of the lachrymal groove, forms the 

 trochleafor the superior oblique muscle of the eyeball, assists the orbital fascia in 

 forming a capsule for the lachrymal gland, and sustains the orbital fat. 



Wliat is tJie first structiire you saw on removing the orbital plate of the 

 frontal bone ? 



The periorbita or orbital periosteum, a continuation of the dura mater 

 through the sphenoidal fissure and the optic foramen. 



On removing the periorbita, wliat did you sec f 



1. In the middle we saw the frontal artery, a branch of the ophthalmic, and 

 the frontal nerve, a branch of the ophthalmic division of the fifth nerve, lying on 

 the levator palpebrae muscle. 



2. To the outer side we saw the lachrymal artery, a branch of the ophthalmic 



