360 THE EAR. 



the sac is of a pale color and soft, and generally found filled 

 with mucus. 



The nasal duct is continuous with and leads from the 

 sac, downward, backward, and outward, covered by the 

 lower turbinated bone, and opening into the inferior mea- 

 tus of the nose below. It is a short canal, about three 

 quarters of an inch in length, a little curved, wider at the 

 centre than at either end, and separated from the antrum 

 by a thin, but strong bony partition. 



Its structure is fibre-mucous; the mucous membrane 

 continued from the sac and lining its interior. 



Blood-vessels. The lachrymal gland is supplied by the 

 lachrymal branch of the ophthalmic artery, and the sac by 

 the nasal branch of the same artery. 



The nerves come from the lachrymal branch of the oph- 

 thalmic and orbital branch of the superior maxillary. 



Blood vessels and Nerves of the Eye and its Appendages. 

 These have been described in the examination of the 

 several parts composing the organ of vision, and we only 

 propose making a single remark by way of refreshing the 

 memory, as applicable to the whole. 



The ophthalmic artery, from the internal carotid, and the 

 facial, temporal, and infra-orbital from the external carotid, 

 are the great sources of arterial supply to the apparatus of 

 sight. The nerves come from the second or optic, the third 

 or motor oculi, the fourth and sixth also motor, the fifth 

 and seventh pair, and from sympathetic branches. See 

 Figs. 73, 74 and 101. 



SECTION II. 

 THE EAR. 



The ear, the organ of hearing, is next in importance of 

 the external senses, in conveying intelligence to the mind; 

 and is the especial organ adapted to receive the impres- 

 sions of sound, and to transmit those impressions to the 

 sensorium. 



Just as we have seen the eye to have special relations with 

 light, and its retina or nervous expansion to be sensible to all 



