164 ANTHROPOLOGY. 



lid along the ocular surface of tlie cartilage, and covered by the mucous 

 membrane ; their openings are seen with a lens as a row of minute pores 

 behind the cilia. They secrete an unctuous fluid which lubricates the 

 edges of the lid and the cilia, prevents their friction and adhesion when 

 closed, and hinders the overflow of tears when these are secreted in mode- 

 rate quantity. 



The conjunctiva^ or internal integument of the palpebrce, lines these cur- 

 tains, and connects them with the eye. At the free edge of each lid, it is 

 continuous Avith the skin. Within the superior lid it ascends, and rises 

 above the cartilage into a cul de sac, the superior palpebral sinus^ which is 

 loosely connected with the cellular and adipose tissue within the orbit, and 

 is then reflected on the fore part of the sclerotic coat of the eye. It iä 

 continued over the cornea as an exceedingly delicate membrane, only sepa- 

 rable by previous maceration. From the lower part of the sclerotic, the 

 conjunctiva is reflected on the inner surface of the lower lid, forming the 

 infe^'ior ptalpehral sinus, and extends to the margin. At the inner canthus 

 of the eye, it forms a vertical fold, the plica semilunaris. The caruncula 

 lachrymalis is a small irregular eminence, placed in the lacus, at the inner 

 canthus of the internal palpebral fissure, internal to the plica semilunaris. 

 It contains a number of minute follicles, which secrete a sebaceous substance 

 which often accumulates in the cornea. 



3. Lachrymaj. Apparatus. This consists of the lachrymal gland and 

 its excretory ducts, the two puncta lachrymalia, the lachrymal canals lead- 

 ing from each into the lachrymal sac, and lastly the nasal duct, leading 

 from the latter into the nose. 



The lachrymal gland is of a pale reddish color, surrounded by a cellular 

 capsule, situated at the upper and outer aspect of the globe of the eye, a 

 position from which its secretion can most effectually flow over the anterior 

 surface of the globe. It consists of two lobes, a superior or orbital and an 

 inferior or palpebral. Six or eight delicate ducts descend nearly parallel 

 from the gland, and open opposite to its lower border by separate orifices 

 on the inner surface of the upper lid, commencing about half an inch from 

 the outer canthus, and a little above the upper margin of the cartilage. 

 This organ secretes the tears which serve to lubricate the eye-ball, and to 

 dilute the more viscid secretion of the mucous membrane. The lachrymal 

 secretion consists of water, and about one per cent, of chloride of sodium 

 (common salt), with a yellow extractive matter. 



The puncta lachrymalia are the two small holes in the cartilaginous 

 })rojections named lachrymal papillge. They are always open and visible to 

 the naked eye, at the inner extremity of the ciliary margin of each carti- 

 lage, and about two lines distant from the inner canthus. Each opening 

 will admit a bristle. They are separated by the caruncula, and each leads 

 into the following. 



The lachrymal canals are two, a superior and an inferior. The superior 

 ascends from the punctum, then bends downwards to the anterior and 

 outer side of the sac. The lower canal just descends, then ascends and 

 opens into the sac very near to the first. 

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