THE LACHRYMAL CAJs^ALS. 



:57 



Fi?. 398. 



THE LACPIRYMAL APPARATUS. 



The parts wliicli constitute the lachrymal apparatus are the follovr- 

 ing, viz. : — The gland by Avhich 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 with the nasal duct continued from it, through which the 

 tears pass into the inferior meatus 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 depressiou in the orbital plate of the frontal bone, 

 to the periosteum of which it adheres by fibrous bands ; the lower sur- 

 face 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 thin layer of fascia, and sometimes described, 

 as a distinct gland {filamhila ladrnjmalis /y?/er/or,Rosenmiiller), is closely 

 adherent to the back of tlie upper eyelid, and is covered on the ocular 

 surface merely by the conjunctiva ; its lobules are small and separate, 

 with minute ducts, some opening separately, others joining the ducts 

 from the principal gLand, which are also very small. The number from 

 both divisions of the gland seldom exceeds twelve or fourteen. After 

 running obliquely under the mucous membrane, and separating at the 

 same time from each other, they open in a row at the fornix conjunc- 

 tivse, by separate orifices, at its 

 upper outer ],iart. In minute 

 structure the lachrymal gland re- 

 sembles the salivary glands. 



Lachrymal canals. — On the 

 margin of each lid, near the 

 inner angle, and in front of the 

 fold of membrane called plica 

 semilunaris, is a small elevation 

 (papilla lachrymalis), as already 

 mentioned. Each papilla is perfo- 

 rated by a minute aperture, j^nnc- 

 tum lachrymale ; and at these 

 apertures commence two narrow 

 canals, canaliculi (fig. 398, 1, 1), 

 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 cor- 

 responding punctum, and then 

 takes a. nearly horizontal course 

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

 unite near the end ; more commonly they open separately, but close 

 together, into the sac. 



Fig. 398. — Front of the Left Evelils, 

 WITH THE Lachrymal Casals asi> 

 Nasal Duct exposed. 



1, 1, upper and lower lachrjniial canals, 

 showing towards tlie eyelids tlie narrow 

 bent portions and the puncta lachrymalia ; 

 '2, lachrymal sac ; 3, the lower part of 

 the nasal duct ; 4, plica semilunaris ; 5, 

 caruncula lachrj-malis. 



