APPENDAGES OF THE EYE. 569 



vertical fold of the mucous membrane plica semilunaris, resting and con- 



r ,, , ,. tiguousfold. 



on the inner part ot the eyeball. 



Blood-vessels of the eyelids. The arteries of the eyelids are Arteries of 

 furnished by the palpebral aud lachrymal branches of the oph- 

 thalmic artery : 



The palpebral arteries, one for each eyelid, run outwards from palpebral 

 llic inner canthus, lying between the tarsal plate and the orbicular 

 muscle, and anastomose externally with the lachrymal artery. From 

 each arch branches are distributed to the structures of the lid. 



The terminal portion of the lachrymal artery perforates the and lachry- 

 palpebral fascia at the outer part of the orbit, and, after having mal - 

 given small offsets to the upper eyelid, divides into two branches 

 which complete the palpebral arches. 



The veins of the lids open into the angular, facial and temporal veins. Veins. 



The nerves of the eyelids are supplied from the ophthalmic and Nerves of 

 superior maxillary divisions of the fifth and the facial nerves. ' s ' 



The branches of the ophthalmic nerve which give offsets to the from fifth, 

 upper lid are the following : lachrymal, at the outer part ; supra- 

 orbital, about the middle ; and sitpratrochlear and infratrochlear 

 at the inner side. In the lower eyelid there are usually two 

 jxfljH'bral branches, inner and outer, of the infra-orbital branch of 

 the superior maxillary nerve. 



Branches of the facial nerve enter both lids at the outer side, and seventh 

 and supply the orbicularis muscle ; they communicate with the nerve> 

 offsets of the fifth nerve. 



THE EXTERNAL EAR. 



EXTERNAL EAR. The outer ear consists of a broad, projecting Parts of 

 part, named the pinna or auricle, and of a tube meatus auditorius externalear - 

 externus, leading inwards to the middle ear, from which it is separ- 

 ated by the tympanic membrane. The pinna may be now examined, 

 but the meatus will be described with the anatomy of the ear. 



The PINNA or AURICLE (fig. 208) is an uneven piece of yellow fibro- Texture and 

 cartilage, which is covered with integument, and is fixed to the margin 

 of the meatus auditorius externus. It is of a somewhat oval form, 

 with the margin folded and the upper end larger than the lower. 



The surface next the head is generally convex ; and the opposite Surface 

 excavated, but presenting the following elevations and depressions. fosLe^uK/ 

 In the centre is a deep hollow named the concha, which is wide above eminences, 

 but narrow below ; it conducts to the meatus auditorius. In front 

 of the narrowed part of the hollow is a projection of a triangular 

 shape the traym, which has some hairs on the inner surface ; and 

 on the opposite side of the same narrow end, rather below the level 

 of the tragus, is placed another projection the antitragus. 



The prominent rim-like margin of the ear, which extends into the Margin, 

 concha, is called the helix; and the depression internal to it is the 

 groove or fossa of the helix. Within the helix, forming the hinder 

 and upper boundary of the concha, is the large eminence of the 

 antihelix, which presents at its upper and fore-part a triangular 

 depression, the fossa of the antihelix. 



