234 



er hairs, to blacken them, that they may still better answer the purpose 

 for which they are intended. 



The eye-lids are two moveable curtains, placed before the eyes which 

 they alternately cover and uncover. It was requisite that they should be 

 on the stretch, and yet capable of free motion ; now, both these ends are 

 obtained by the tarsal cartilages, which are situated along the whole of 

 their free edges, and of the muscles which enter into their structure*. 

 The cellular tissue, which unites the thin and delicate skin of the eye-lids 

 to the muscular fibres, contains, instead of a consistent fat, which would 

 have impeded its motion, a gelatinous lymph, which, when in excess, 

 constitutes oedema of the eye-lids. The tissue of the eye-lids is not abso- 

 lutely opaque, since, even when strongly drawn together, and completely 

 covering the globe of the eye, one may still discern through their texture, 

 light from darkness. On that account, light may be considered as one of 

 the causes of awakening, and it is of consequence to keep in the dark, 

 patients fatigued by want of sleep. 



The principal use of the eye-lids is to shade the eyes from the continu- 

 al impression of light. Like all the organs, the eyes require to recruit 

 themselves by repose; and they had not been able, to enjoy it, if the in- 

 cessant impression of the luminous rays had continually excited their 

 sensibility. The removal of the eye-lids t is attended with loss of sleep. 

 The fluids are determined to the affected organ which suffers from in- 

 cessant irritation. The eyes inflame, the inflamation spreads towards the 

 brain, and the patient expires in the most dreadful agony. Thanks to an 

 advanced state of civilization, these barbarous tortures have long been 

 abolished ; but what happens, when from ectropium of one or other of 

 the eye-lids, a small portion of the sclerotic coat or cornea remains un- 

 covered, proves the indispensable necessity of those parts. The spot ex- 

 posed to the continued action of the air and of the light, becomes irritat- 

 ed and inflamed, and there comes on an ophthalmia, which can be cured 

 only, by bringing together, by means of a surgical operation, the divided 

 edges of the opening which is the cause of the affection. From the move- 

 able edges of both eye-lids, there arise short curved hairs, of the same 

 colour as those of the eye-brows; they are called eye-lashes, and are in- 

 tended to prevent insects, or other very light substances, floating in the 

 atmosphere, from getting between the eye-ball and the eye-lidst. 



The anterior part of the eye, thus defended against external injuries, 

 is continually moistened by the tears. The organ which secretes this 

 fluid, is a small gland situate in a depression at the anterior and external 

 part of the arch of the orbit, imbedded in fat, and supplied with pretty 

 considerable vessels and nerves in proportion to its bulk, and pouring the 

 fluid it secretes, by means of seven or eight ducts which open on the 

 internal surface of the upper eye-lid, by capillary orifices directed down- 

 ward and inward. The tears are a muco-serous fluid, rather heavier than 



* Dr. Horner of Philadelphia, has lately discovered a beautiful muscle arising from the 

 os unguis, and inserted into the cartilage of the upper and lower lids, as far as the punc- 

 ture and commencement of the lachrymal duct. The office of this muscle seems to be 

 that of tightening the edge of the cartilages so as to apply them closely to the ball of the 

 eye. He has named it Tensor Tarsi. See his Practical Anatomy, p. 116. Godman. 



f A mode of punishment adopted by the ancients, especially the Carthaginians. 



* They also absorb and intercept some of the luminous rays, and thus diminish the 

 hurtful effects of too strong a light. 



