AURICLE OF THE EAR. 45 



minute lateral caeca! appendages connected with it. Each contains a seba- 

 ceous secretion, and is lined by flattened epithelium. 



If the palpebral ligament be cut through in the upper lid, the tendon of 

 the levator palpebree will be seen to be inserted into the fore part of the 

 tarsal cartilage by a wide aponeurotic expansion. 



The conjunctiva, or the mucous membrane, lines the interior of the 

 eyelids, and covers the anterior part of the ball of the eye. Inside the 

 lids it is inseparably united to the tarsal cartilages, and has numerous fine 

 papillae. At the free margin of the lid this membrane joins the common 

 integuments. Through the lachrymal canals and sac it is continuous with 

 the pituitary membrane of the nose. 



At the inner commissure of the eyelids the conjunctiva forms a promi- 

 nent and fleshy-looking body caruncula lachrymalis (fig. 13, 4 ), which 

 contains a group of mucous follicles, and has a few minute hairs on its 

 surface. External to the caruncle is a small vertical fold of the mucous 

 membrane plica semilunaris ; this extends to the ball of the eye, and 

 represents the membrana nictitans of birds. 



Bloodvessels of the eyelids. The arteries of the eyelids are furnished 

 by the ophthalmic artery, and come from the palpebral and lachrymal 

 branches : 



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

 canthus, lying between the tarsal cartilage and the tendon of the special 

 elevator in the upper lid, and between the cartilage and the palpebral liga- 

 ment in the lower lid ; and they anastomose externally with the lachrymal 

 artery. From the arch that each forms, branches are distributed to the 

 eyelids. 



The lachrymal artery furnishes an offset to each lid to form arches with 

 the palpebral arteries, and then perforates the palpebral ligament at the 

 outer part of the orbit to end in the upper lid. 



The veins of the lids open into the frontal and angular veins at the root 

 of the nose (pp. 21, 40). 



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

 nerves. 



The branches of the ophthalmic nerve (of the fifth) which give offsets 

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

 orbital, about the middle ; and supra-trochlear and infra-trochlear at the 

 inner side (pp. 42, 54). In the lower eyelid, about its middle, is & palpe- 

 bral branch of the superior maxillary trunk of the fifth nerve. 



Branches of the facial nerve (p. 48) enter both lids at the outer part, 

 and supply the orbicularis muscle ; they communicate with the offsets of 

 the fifth nerve. 



EXTERNAL EAR. The outer ear consists of a trumpet-shaped structure, 

 named pinna or auricle, which receives the undulations of the air ; and of 

 a tube meatus auditorius, which conveys them to the inner ear. The 

 pinna may be examined on the left side of the head ; but the anatomy of 

 the meatus will be described with the ear. 



The pinna, or auricle, is an uneven piece of yellow fibro-cartilage, 

 which is covered with integument, and is fixed to the margin of the meatus 

 auditorius externus. It is of an oval form, with the margin folded and 

 the larger end placed upwards. 



The surface next the head is generally convex ; but the opposite is ex- 

 cavated, and presents the undermentioned elevations and depressions. In 

 the centre is a deep hollow named concha, which is wide above but narrow 



