LACHRYMAL APPARATUS SG7 



glands. The palpebral lymphatic vessels niainl}- pass through the jn-eauricular 

 gland; but, sometimes at least, those from the inner half of the lower lid go to the 

 submaxillary lymphatic glands. 



Nerves. — (a) Sensory. The upper lid is chiefly supplied by l)ranches of the 

 supraorVjital and supratrochlear nerves, the lower lid by one or two l^ranches of 

 the infraorbital. At the inner canthus the infratrochlear nerve also aids in the 

 supply, and, at the outer canthus, the lachrymal. (6) Motor. The palpebral part 

 of the orbicularis is supplied l:)y branches of the facial nerve, which mainly enter 

 it near the outer canthus. Miiller's palpebral nmscles are supplied by the sympa- 

 thetic nervous system. 



The inner palpebral ligament, or tendo oculi, has been referred to previously. 

 Arising from the frontal process of the maxilla, it extends outwards over the 

 front wall of the lachrymal sac, bends round the outer wall of the sac, and then 

 passes liackAvards to the posterior crest on the lachrymal bone. It is thus U-shaped, 

 having its limbs anterior and posterior, embracing the lachrymal sac; the anterior 

 limb lies immediately beneath the skin, and is visible in the living. The palpei)ral 

 fibres of the orbicularis are inserted into the outer surface of both limbs, those 

 attached to the posterior limb constituting Horner's muscle. The outer palpe- 

 bral ligament is merely a stronger development of connective tissue in the orbicu- 

 laris. Both ligaments are connected with the tarsi as already mentioned. 



The Lachrymal Apparatus 



The tears are secreted by an acinous gland, and flow through fine ducts to the 

 upper outer part of the conjunctival sac, whence they are drained off through the 

 puncta, pass along the canaliculi into the lachrymal sac, and ultimately run down 

 the nasal duct to gain the inferior meatus of the nose. 



The lachrymal gland is situated near the front of the outer part of the roof of 

 the orbit, lying in a depression in the orbital plate of the frontal bone. It consists 

 of two very unequal parts, one placed above and the other beneath the tendinous 

 exi^ansion of the levator palpel^rse superioris, but small gaps in the expansion 

 permit of connections between these two parts of the gland. The upper and larger 

 subdivision {superior lachrymal gland) is a firm elongated body, al^out the size of 

 a small almond; it has a greyish-red colour, and is made up of closely aggregated 

 lobules. The upper surface (next the orbital roof) is convex, and its lower surface 

 is slightly concave. Anteriorly, the gland almost reaches the upper orbital mar- 

 gin, and it extends backwards for approximately one-fourth the depth of the 

 orbit, measuring about twelve millimetres in this direction. The outer border oi 

 the gland descends to near the insertion of the fascial expansion of the external 

 rectus, while its inner border almost reaches the outer edge of the superior rectus; 

 its transverse measurement is al)out twenty millimetres. It is enveloped in a 

 capsule, which is slung by strong fibrous bands passing to its inner border from 

 the orbital margin (suspensory ligament of the gland). 



The lower subdivision of the gland (inferior lachrymal gland) is composed oi 

 loosely applied lobules, and lies immediately over the outer third of the up])er 

 conjunctival fornix, reaching outwards as far as the external canthus. 



Each subdivision of the gland jiossesses several excretory ducts, Avhich all open 

 on the outer part of the upper fornix conjunctivse, about four millimetres above tlie 

 upper border of the tarsus. Those of the superior gland, three or four in number, 

 pass between the lobules of the lower gland; the outermost duct is the largest, and 

 opens at the level of the external canthus. The ducts of the inferior gland in part 

 discharge themselves into those of the upper, but there are also several line ducts 

 from this subdivision that run an independent course. 



Near the inner canthus are the two puncta lachrymalia, upjierand lower, each 

 situated at the summit of its pajnlla. The to]) of each pai)illa curves backwards 

 towards the conjunctival sac, so that the i)uncta are well adapted for their function 

 of draining off any fluid collecting there. 



The canaliculi lachrymales <-xtend from tlie puncta to the lachrymal .^ac. 

 The lumen at the punetuni is horizontally oval, from its lips being slightly com- 



