THE LACHRYMAL APPARATUS. 417 



margins of the lids. Each duct, with its lateral crypts, resembling 

 rows of onions on a string, consists of a membranous wall, lined with 

 a glandular epithelium, which secretes a sebaceous matter. In the 

 upper lid, there are about thirty glands ; in the lower lid, from fifteen 

 to twenty, and they are much shorter. 



Pig. 78. 



Fig. 78. A portion of the margin of the upper eyelid, showing a fw of the Meibomian glands attached 

 to it. a, orifices of the central ducts of each gland, b, rows of follicles or sacs, arranged upon each central 

 duct. 



The elliptical interval between the opened eyelids, is called the 

 palp ebral fissure ; the outer and inner angles of this fissure, are named 

 the canthi. At the outer canthus, the bevelled margins of the lids, 

 form an acute angle ; but at the inner canthus, the margins, which are 

 here rounded, are separated by a small interval, called the lacus 

 lachrymalis, the lachrymal lake or pit, Fig. 79. Along the margins 



Fig. 79. 



Fig. 79. Front of the eyeball and its appendages. 1, dotted outline, showing the position, size, and shape 

 of the lachrymal gland. 2. similar outline, showing the form and position of the lachrymal sac and nasal 

 duct. On the left hand of this, other dotted lines indicate the course of the two lachrymal canaliculi, lead- 

 ing into the sac, one above, and one below, the lachrymal lake or sinus, which is occupied by the caruncle ; 

 between the caruncle and the eyeball, is the edge of the rudimentary nictitating membrane. The asterisk * 

 indicates the orifice of the lower canaliculus, named the inferior lachrymal punctum. The orifices of the 

 Meibomian glands, are seen in the margin of the lower eyelid The white exposed part of the eyeball, cor- 

 responds with a portion of the sclerotic coat of the eye. The circular dark-colored part represents the iris, 

 perforated by the pupil, and covered by the transparent coat or cornea. 



of the eyelids, are two or more rows of finely-curved hairs, named the 

 cilia or eyelashes; in the upper lid, they are more numerous, thicker, 

 and longer than in the lower lid ; the lashes of the upper lid curve 

 upwards, those of the lower lid downwards, so that they do not interlace 

 when they meet or separate. At the inner canthus is placed a soft 

 red fleshy-looking eminence, the caruncle, from caro, flesh ; it is made 



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