LACHRYMAL GLANDS AND CANALS. 709 



THE LACHRYMAL APPARATUS. 



The parts which constitute the lachrymal apparatus are the following, 

 viz. : The gland by \\hich the tears are secreted, situated at the upper and 

 outer side of the orbit, together with its excretory ducts ; the two canals 

 into which the fluid is received near the inner angle ; and the sac wuh the 

 nasal duct continued from it, through which the teard pass into the inferior 

 meat us of the nose. 



The lachrymal gland, an oblong flattened body, about the size of a small 

 almond, is placed in the upper and outer part of the orbit, a little behind 

 the anterior margin. The upper surface of the gland, convex, is lodged in a 

 slight depression in the orbital plate of the frontal bone, to the periosteum 

 of which it adheres by fibrous bands ; the lower surface is adapted to the 

 convexity of the eyeball, and is in contact with the upper and the outer 

 recti muscles. The fore part of the gland, separated from the rest by a 

 slight depression, and sometimes described as a second lobe, or as a distinct 

 gland, is closely adherent to the back of the upper eyelid, and is covered on 

 the ocular surface only by a reflection of the conjunctiva. The glandular 

 ducts, usually from six to eight in number, are very small, and emerge from 

 the thinner portion of the gland. After running obliquely under the mucous 

 membrane, and separating at the same time from each other, they open in a 

 row by separate orifices, the greater number in the fold above the outer 

 cauthus, and two of them (Hyrtl) in the fold below. 



Fig. 458. FRONT OP THE LEFT EYELIDS, p. ._ 



WITH THE LACHRYMAL CANALS AND NA- *>' 



SAL DUCT EXPOSED. 



1,1, upper and lower lachrymal canals, 

 showing towards the eyelids the narrow 

 bent portions and the puncta lachrymal ia ; 

 2, lachrymal sac ; 3, the lower parjb of the 

 uasal duct ; 4, plica semilunaris ; 5, ca- 

 runcula lachrymalis. 



Lachrymal canals. On the mar- 

 gin of each lid, near the inuer 

 angle, and in front of the fold of 

 membrane called plica semilunaris, 

 is a small elevation (papilla lachry- 

 malis), already described. Each 

 papilla is perforated by a small 

 aperture, punctum lachrymale ; and 



at these apertures commence two small canals, canaliculi, which convey 

 the tears from the eye to the lachrymal sac. The upper canal is rather 

 the smaller and longer of the two : it first ascends from the punctum ; then 

 makes a sudden bend, and is directed inwards and downwards to join the 

 lachrymal sac. The lower canal descends from the corresponding punctum ; 

 and soon changing its direction like the upper one, takes a nearly horizontal 

 course inwards. Both canals are dilated where they are bent. In some 

 cases they unite near the end to form a short common trunk ; more 

 commonly they open separately, but close together, into the sac. 



The lachrymal sac and nasal duct constitute together the passage by which 

 the tears are conveyed from the lachrymal canals to the cavity of the nose. 



