262 



ANATOMY OF VERTEBRATES. 



208 



Lacrymal gland, left 

 Bide. ex". 



depressor. The outer border of the ciliary margin of both 

 lids is provided, in Man, with eye-lashes, fig. 207, the orifices of 

 which, when plucked out, are shown at h, fig. 206. In this 

 figure b is the c outer canthus,' c the * inner canthus,' d lacrymal 

 papilla or ( punctum ' of the upper lid ; e, the same of the lower 

 lid ; f, the lacrymal caruncle ; g, the semilunar fold representing 

 the ■ third eyelid,' and now forming the bottom of the s lacus 

 lacrymalis ' within the fissure of the inner canthus ; i, the eye- 

 brow. In the section of the outer parts of the eyelids, in fig. 

 207, is shown the line of reflection of the con- 

 junctive membrane upon the eyeball, g, at the 

 upper and outer part of which line open the 9 to 

 12 orifices of the ducts of the lacrymal gland, into 

 which bristles have been inserted. 



The gland, fig. 208, consists of an upper por- 

 tion a, a, which is lodged in the shallow depres- 

 sion at the outer side of the roof of the orbit, 

 and a lower thinner portion, b, b, which is a looser 

 aggregate of lobules extending into the substance 

 of the upper eyelid. The fluid contributed by 

 the lacrymal and meibomian glands to the conjunctival cavity, 

 after being spread by the winking movements of the lids over 



the front of the eyeball, is carried 

 along the groove formed by the 

 margins of the closed lids to the 

 inner canthus, and is there im- 

 bibed by the ' puncta lacrymalia,' 

 fig. 209, a, a. From each of these 

 orifices a canal is continued, ascend- 

 ing in the upper, descending in the 

 lower lid ; in both, then, bending at 

 an acute angle and converging to a 

 long dilated receptacle, f, g, called 

 ' lacrymal sac' The large blind 

 end, e, is directed upward ; the sac 

 gradually contracts, h, to the ' nasal 

 duct,' z, which opens into the infe- 

 rior meatus, fig. 152, k, of the nose. 

 In all Mammals with divided or horizontal eyelids there is a 

 similar provision for carrying off the waste lubricating fluid of the 

 eyeball. In Man, in whom the true lacrymal gland is relatively 

 largest, its peculiar secretion — the tears — when emotionally 

 secreted in excess, overflows the palpebral groove. 



209 



Lacrymal apparatus, Human, ex". 



