834 TBE APPABATUS OF THE SENSES. 



LACHRYMAL APPABATUS. 



" This apparatus comprises : 1, A gland which. secretes the tears ; 2, A 

 series of canals that carry the superfluous fluid to the external orifice of the 



nasal cavities. -i , . , 



" Lachrymal gland. — This gland, situated between the orbital process and 

 the upper part of the eyeball, from which it is separated by the superior 

 rectus and levator palpebrs muscles, is convex on its upper face, and concave 

 inferiorly, in accordance with the parts it adjoins. But little developed, it 

 is formed' of very small granulations, united by fine connective tissue ; from 

 these arise minute radicles, whose junction forms a certain number of very 

 narrow ducts which open on the inner face of the temporal (outer) angle of 

 the eyelids. These are the Jiygrophthalmic canals. 



" The lachrymal gland secretes the tears destined to lubrify the anterior 

 surface of the eye. This fluid escapes upon the organ at the temporal angle 

 of the lids, and is carried between them and the eyeball towards the nasal 

 angle. Its secretion is incessant, but it is increased by anything that 

 irritates the conjunctiva, and its character may even change under the same 

 influences. 



" The lachrymal gland belongs to the category of conglomerate glands ; 

 consequently, it is analogous to the salivary glands. ( The gland is maintained 

 in situ by a capsule formed by the fascia of the orbit.) 



" The hygrophthalmic canals have a thin fibrous membrane for their 

 walls ; this is covered by cylindrical epithelium. 



" Caruncula lacJirymalis. — This name is given to a small round (or fusi- 

 form) body, frequently entirely, or partially black (or brown), slightly 

 uneven, and situated in the nasal angle of the eye ; it is nothing more than 

 a small fold of conjunctiva covering some agglomerated follicles, and 

 the bulbs of several fine hairs, which are readily seen on its surface. It 

 may be regarded as designed to direct the tears towards the punota, or to 

 separate the extraneous particles that this fluid may carry towards it. 



" It has for its base a small mass of connective tissue, in the midst of 

 which are some hair-roots, and some rather large glandules, lined by an 

 epithelium charged with fat granules. Nerve-tubes ramify around the hair 

 bulbs. 



" Puncta lacJirymaHa. — These are two little openings, situated one in each 

 eyelid, a short distance from the nasal commissure, by which the tears pass 

 from the oculo-palpebral surface into the lachrymal ducts. 



" Lachrymal ducts. — These are continuations of the last, and, like them, 

 are very narrow ; they carry the tears into the lachrymal sac. The superior 

 is longer than the inferior duct, and arrives at the sac behind it. The 

 mucous membrane lining these ducts is thin, and covered by a stratified 

 pavement epithelium, similar to that of the conjunctiva. 



" Lachrymal sac. — This little reservoir, lodged in the infundibulum that 

 precedes the lachrymal foramen in the bone of that name, receives the tears 

 from the two ducts, and passes them into the lachrymal canal. Its mucous 

 membrane only differs from that of the ducts in being covered with ciliated 

 epithelium. 



" Lachrymal canal [nasal duct). — The tears accumulated in the sac flow 

 into this long duct, which extends to the lower aperture of the nostril. 

 About one half of its course is in the osseous canal of the lachrymal bone 

 which protects it, and which terminates between the two turbinated bones. 

 The remainder of the canal is beneath the nasal mucous membrane, whence 



