i LACHRYMAL APPARATUS. 697 
of the outer canthus they anastomose with each other and with twigs from the lachrymal, super- 
ficial temporal, and transverse facial arteries, and in this way an arch is formed in each hd (upper 
and lower tarsal arches). Secondary smaller arches are found, one above the primary arch in the 
upper lid and another below that of the lower lid, while the upper lid also receives branches from 
the supraorbital and frontal arteries. The veins are arranged into two sets: (@) subconjunctival 
or retrotarsal, opening into the muscular tributarie: of the ophthalmic vein, and ()) pretarsal, which 
pour their contents into the angular and superficial temporal veins. The lymphatics, like the 
veins, form pre- and retrotarsal networks, which communicate with each other through the tarsal 
plates. The lymph is drained partly into the preauricular and parotid lymphatic glands, and 
partly, by vessels which accompany the facial vein, into the submaxillary lymphatic glands. The 
sensory nerves of the eyelids are supplied by the fifth cranial nerve—the upper lid chiefly by the 
supraorbital and supratrochlear branches of the ophthalmic ; the lower, by the infraorbital branch 
of the superior maxillary. The region of the outer canthus receives some filaments from the 
lachrymal nerve, that of the inner from the infratrochlear. These sensory nerves form a marginal 
plexus behind the orbicularis palpebrarum muscle. The levator palpebre muscle is supplied by 
the third cranial nerve and the non-striped fibres of the lids by the sympathetic. 
LACHRYMAL APPARATUS. 
The lachrymal apparatus (apparatus lacrimalis) consists of: (1) the lachrymal 
gland, which secretes the tears; (2) the lachrymal canals, by which they are drained 
from the front of the globe; and (3) the lachrymal sac and nasal duct, which convey 
them into the nasal cavity. 
The lachrymal gland is a flattened, oval body situated in the upper and outer 
part of the orbital cavity, and consists of two portions—orbital and palpebral— 
unperfectly separated from each other by the expansion of the tendon of the levator 
palpebrzsuperioris muscle. The orbital portion, termed the glandula lacrimalis superior, 
is firm and much larger than the palpebral part; it measures transversely about 
20 min., and sagittally from 12-14mm. It occupies the fossa lacrimalis on the inner 
aspect of the external angular process of the frontal bone and is fixed by fibrous 
bands to its periosteum, while its inferior surface is in contact with the levator 
palpebre superioris and external recti muscles which intervene between it and the 
globe of the eye. The smaller, palpebral portion, named glandula lacrimalis inferior, 
consists of loosely agerevated lobules. It lies below and in front of the orbital 
portion and projects into the posterior part of the upper eyelid, where its deep sur- 
face is in contact with the conjunctiva. The ducts of the upper gland, from three 
to five in number, receive those of the lower gland, which vary from three to nine, 
and open on the upper eyelid close to the fornix conjunctive superior. The 
lachrymal gland has a structure similar to that of the parotid, and is supphed by 
the sympathetic and lachrymal nerves and by the lachrymal artery, while its veins 
are drained into the ophthalmic vein. 
The lachrymal canals (ductus lacrimales) commence by minute orifices, termed 
the puncta lacrimalia, at the apices of the papillie lacrimales, already referred to (p. 
695). The upper canal is the smaller of the two, and at first ascends for a short 
distance, and then runs inwards and slightly downwards; the lower descends for a 
short distance and then runs horizontally inwards. At the angle where they 
change their direction each is dilated into an ampulla (ampulla ductus lacrimalis). 
They occupy the margins of the lids, where these bound the lacus lacrimalis, and 
the two canals open close together into the outer and forepart of the lachrymal 
sac, a little below its middle; sometimes they open separately into a pouch-like 
dilatation of the sac, termed the sinus of Maier. Each canal is lined by a 
stratified epithelium placed on a tunica propria, outside which is a layer of 
striped muscular fibres, derived from the tensor tarsi muscle. These muscular 
fibres are arranged somewhat spirally around the canals, but at the bases of 
the papille they are circular in direction and form a species of sphincter. On 
contraction, they serve to empty the contents of the lachrymal canals into the 
lachrymal sac. 
The lachrymal sac and nasal duct together form the passage by which the tears 
are conveyed from the lachrymal canals to the nose. 
The lachrymal sac (saccus lacrimalis) is the upper expanded part of the passage, 
and measures from 12-15 mm. in length, about 7 mm. antero-posteriorly, and 
from 4-5 mm. transversely. It lies in the groove formed by the lachrymal bone 
