840 ORGANS OF SPECIAL SEXSE 



movements of the eyeball, being greatest on looking strongly upwards, diminishing 

 gradually as the eye looks progressively lower. The angles formed l)y the meeting of 

 the lids at each end of the palpebral aperture are named respectively the outer and 

 inner canthus, of which the outer, or temporal, is sharp, while the inner, or nasal, 

 is rounded off. On a closer inspection, it will be found that, for the last five milli- 

 metres or so before reaching the inner canthus, the edges of the lids run an almost 

 parallel course, and are here devoid of lashes. Through the open palpel^ral aperture 

 the front of the eyeball comes into view, extending quite to the outer, but not reach- 

 ing as far as the inner, canthus; just within the latter we find a small reddish 

 prominence, the lachrymal caruncle ; an<l lietween this and the eyeball a fold of 

 conjunctiva known as the plica semilunaris, ^^'hile the eye is open, press one 

 finger on the skin, a little beyond the outer canthus, and draw it firmly outwards 

 from the middle line; observe that the upper lid then falls over the eyeball, and 

 that the outline of a firm band already referred to (the tendo oculi) becomes 

 evident, passing between the inner canthus and the nose. The falling of the lid is 

 caused by our dragging upon a ligament (the outer jialpebral) to which the outer 

 end of its tarsus is attached, and so putting the lid itself u])on the stretch. If, 

 while the eyeball is directed downwards, we place one finger on the outer end of the 

 up})er eyelid and draw it forci])ly upwards and outwards, we can usually cause the 

 lower division of the lachrymal gland to present just above the outer canthus. 



The upper eyelid is much broader than the lower, extending upwards as far as 

 the eyebrow. The skin covering it is loosel}' attached to the subjacent tissues above, 

 but more firmly below^, nearer the free margin, Avhere it overlies a firm fibrous 

 tissue called the tarsus. When the eye is open, a fold is present at the upper border 

 of this latter more tightly applied portion of skin, called the superior palpebral 

 fold, and by it the lid is marked off into an upper or orl)ital, and a lower or tarsal, 

 division. The presence of the tarsus can be readily appreciated on our pinching 

 horizontally the entire thickness of the eyelid below the palpebral fold. The lower 

 eyelid is similarly divided anatomically into a tarsal and an orbital part, l)ut the 

 demarcation is sometimes unrecognisable on the surface, though there is usually 

 here also a fold or groove (the inferior palpebral) visible when the eye is Avidely 

 opened. There is no precise limit of this lid Ijelow, but it may be regarded as 

 extending to the level of the lower margin of the orl)it. Numerous very fine short 

 hairs are seen on the cutaneous surface of both eyelids. The free margin of each 

 lid has two edges — (a) An outer, or anterior, rounded edge, along which the stiff 

 eyelashes, or cilia, are closely placed in several rows; and (b) a sharp jtosterior 

 edge, which is applied to the surface of the globe. The lashes of both eyelids have 

 their points turned away from the palpebral aperture, so that the u|)per ones curve 

 upwards, and the lower downwards; the cilia of the upper lid are the stronger, and 

 those in the middle of each row^ are longer than those at each end. Between the 

 tw^o edges just described, the lid-margin has a smooth surface, on which we observe 

 a single row of minute apertures, Avhich are the openings of large modified sebaceous 

 glands (the Meibomian follicles) ; it is by these glistening, well -lubricated sur- 

 faces that the ojiposite lids come into apposition when they are closed. The sharj) 

 l)Osterior edge of the lid-margin marks the situation of the transition of skin into 

 mucous membrane. Not far from the inner end of this edge we find a ])rominence, 

 the lachrymal papilla, on the summit of which is a small hole (lachrymal punc- 

 tum), the opening of the canaliculus for the passage of tears into the lachrymal 

 sac. The lower punctum is rather larger than the up])er, and is placed further 

 from the inner canthus. 



If we now examine the inner surface of the eyelids — e.g. of the lower — we 

 observe that it is lined by a soft mucous membrane, the palpebral conjunctiva. 

 Over the tarsal part of the lid, the conjunctiva is closelv adherent, but beyond this 

 it is freely movable along with the loose subniucous tissue here present. On 

 tracing it backwards, we find that it covers the whole inner surface of the lids, and 

 is then continued forimnh over the front of the eyeliall, forming the ocular 

 conjunctiva; the bend it makes as it changes its direction here is called the con- 

 junctival cul-de-sac, or fornix. Numerous underlying blood-vessels are visible 

 through the palpeliral conjunctiva, and beneath the tarsal part of it we can see 

 a series of nearly straight, parallel, light yellow lines, arranged per])endicularly 



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