FACE AND FRONTAL REGION OF HEAD 27 



and zygomatic branches of the facial nerve. They enter 

 from the lateral margins. The sensory twigs for the upper 

 lid come from the lacrimal, supra-orbital, supra-trochlear, and 

 infra-trochlear branches of the first or ophthalmic division of 

 the trigeminal nerve; and the lower lid is supplied by the 

 infra-orbital branch of the maxillary division of the fifth 

 cerebral nerve. The lacrimal nerve will be found piercing 

 the palpebral fascia near the lateral part -of the upper border 

 of the orbit ; the supra-orbital lies in the supra-orbital notch 

 at the junction of the lateral two-thirds with the medial third 

 of the upper border ; and the supra- and infra-trochlear pierce 

 the palpebral fascia at the medial end of the upper border. 

 The branches of the infra-orbital nerve pass to the lower lid 

 in the palpebral branches of the infra-orbital plexus (p. 20). 



Apparatus Lacrimalis. The following structures are in- 

 cluded under this head : (i) the lacrimal gland and its- ducts ; 

 (2) the conjunctival sac ; (3) the puncta lacrimalia ; (4) the 

 lacrimal ducts; (5) the- lacrimal sac; (6) the naso-lacrimal 

 duct ; (7) the lacrimal part of the orbicularis oculi. 



Glandula Lacrimalis. The lacrimal gland lies in the 

 upper and lateral part of the orbital cavity, under cover of 

 the zygomatic process of the frontal bone. It can be exposed 

 by cutting through the palpebral fascia at the upper and lateral 

 angle of the orbit, and it will be found that the anterior part 

 of the gland projects slightly beyond the orbital margin and 

 rests upon the conjunctiva, as the latter is reflected from the 

 lateral part of the upper lid on to the eyeball. If the anterior 

 border of the gland is raised and the point of the knife 

 is carried carefully up and down in the fascia under it, several 

 exceedingly fine ducts will be found passing from the gland 

 into the lateral part - of the upper fornix of the conjunctiva 



(Fig. 9)- 



The ducts vary in number, and the secretion they 

 convey, which constitutes the tears, is carried, by the in- 

 voluntary movements of the upper eyelid, over the exposed 

 surface of the eyeball and is directed towards the medial 

 commissure ; there it passes through the puncta lacrimalia 

 into the lacrimal ducts, and is carried by them to the lacrimal 

 sac, whence it passes by the naso-lacrimal duct into the 

 inferior meatus of the nose. Under ordinary circumstances, 

 the amount of lacrimal secretion is sufficient merely for lubrica- 

 tion, and practically the whole of it is evaporated from the 



