THE EYE AND ITS APPENDAGES 237 



The inferior or cochlsar branch is distributed to : 



1. The cochlea. 



2. The saccule. 



3. The ampulla of the posterior semicircular canal. 

 Nerves of the Cochlea. The branches of the auditory nerve 



destined for the cochlea perforate a number of foramina at 

 the bottom of a spiral groove, the tractus spiralis foraminulen- 

 ttis, placed in the centre of the base of the cochlea. These 

 foramina lead to small canals, which at first pass through the 

 modiolus, and then radiate outwards between the bony layers 

 of the lamina spiralis, so passing to the organ of Corti. In 

 the centre of the tractus spiralis foraminulentus is a larger 

 foramen leading to the central canal of the modiolus, and 

 transmitting nerve filaments for the last half-turn of the 

 cochlea. 



THE EYE AND ITS APPENDAGES. 



THE APPENDAGES OF THE EYE. 



The eye-brows are two arched eminences over each orbit 

 consisting of thickened integuments and muscles, surmounted 

 by hairs. 



The eye-lids are two movable folds, an upper and a lower, 

 the upper one being more movable, which by their closure 

 protect the eye from injury. When the eye-lids are open the 

 angles of junction of the upper and lower lids are called re- 

 spectively the external and the internal canthus. In the inner 

 canthus the lids are separated by a small triangular area, the 

 lacus lachrymalis, in which is seen a pink mass of fat and 

 connective - tissue, the caruncula lachrymalis, and which is 

 separated from the eye-ball by a vertical fold of conjunctiva, 

 the plica semilunaris, a rudimentary third eye-lid; opposite the 

 outer edge of the caruncle, on each lid, is the lachrymal papilla, 

 which is pierced by the punctum lachrymals, the external open- 

 ing of the lachrymal canal. 



Structure from without inwards : skin, areolar tissue, orbicu- 

 laris muscle (p. 22), tarsal plate, and palpebral ligament, 

 Meibomian glands, and conjunctiva; the upper lid also con- 

 tains the aponeurosis of the levator palpebrse, which is 

 'attached along the upper margin of the tarsal plate. 



The tarsal plates are laminae of condensed connective- 

 tissue found in each lid ; the superior, the larger, is half oval 



