138 HEAD AND NECK 



infra-orbital branch of the second or maxillary division of the 

 fifth 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. 128). 



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. This lies in the upper and lateral 

 part of the orbital cavity under cover of the zygomatic process 

 (O.T. external angular) 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 

 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. 

 The ducts vary in number, and the secretion which 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 merely sufficient for lubrica- 

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

 surface of the eyeball ; consequently, when the lacrimal ducts 

 and the lacrimal sac are extirpated, a proceeding which is 

 necessary under certain circumstances, the patient suffers 

 little or no inconvenience from the overflow of tears, so long 

 as the secretion is not excessive. If the amount of secretion 

 is greater than can be removed by evaporation, the excess, 



