THE ORBIT 247 



along the lateral wall of the cavity, above the upper margin 

 of the lateral rectus muscle. At the anterior part of the 

 orbit it continues its course, under cover of the lacrimal gland, 

 until it reaches the lateral part of the upper eyelid, in which 

 it ends (p. 27). Within the orbital cavity it gives numerous 

 twigs to the deep surface of the lacrimal gland, and sends 

 downwards a filament which connects it with the zygomatic 

 branch of the maxillary nerve. 



Nervus Trochlearis. The small troqhlear nerve is destined 

 entirely for the supply of the superior oblique muscle. Having 

 entered the orbit through the superior orbital fissure, above the 

 muscles, it passes forwards and medially, under the periosteum, 

 and finally sinks into the posterior part of the upper or orbital 

 surface of the superior oblique muscle. 



GlandulaLacrimalis. The lacrimal gland is a small, flattened 

 and distinctly lobular structure, of oval form, which is placed 

 in the antero-lateral part of the orbit, its long axis lying 

 parallel with the anterior margin of the orbit (Figs. 92, 97). It 

 consists of two parts or groups of lobules a superior and an 

 inferior imperfectly separated from each other. Tbeglattdttla 

 lacrimalis superior, which constitutes the main mass of the gland, 

 lies in the orbital cavity. Its lateral convex surface is lodged 

 in a hollow upon the medial aspect of the zygomatic process 

 of the frontal bone, and it is bound to the lateral part of the 

 orbital arch by short fibrous bands which proceed from the 

 periosteum. The deep or medial surface is slightly concave, 

 and rests upon the levator palpebrae superioris and lateral 

 rectus, which intervene between it and the eyeball. The 

 glandula lacrimalis inferior lies below and anterior to the 

 superior part, from which it is partially separated by the ex- 

 panded tendon of the levator palpebrse superioris. It projects 

 into the base of the. upper eyelid, and rests upon the con- 

 junctiva which lines the deep aspect of the lid. That portion 

 of the gland has been already examined in the dissection of 

 the eyelids (p. 27). Even in the undissected subject it can 

 be seen, through the conjunctiva, when the upper eyelid is 

 fully everted. 



The lacrimal gland secretes the tears, and its ducts 

 (three to five from the superior part and three to nine from 

 the inferior part) open upon the deep surface of the upper 

 eyelid in the neighbourhood of the fornix (Fig. 9). 



Musculus Levator Palpebrse Superioris. The elevator 



