376 INTERNAL EAR OR LABYRINTH. 



modiolus, and between the plates of the lamina spiralis. 

 The posterior branch divides into the superior, middle, and 

 inferior. The superior filaments enter the vestibule through 

 the small foramina of the pyramid, and are expanded on 

 the sacculus communis, and ampullce of the superior verti- 

 cal, and horizontal membranous canals. The middle set 

 supply the sacculus proprius, and the inferior go to the 

 ampulla of the posterior vertical semicircular canals. The 

 auditory nerve is remarkable for its softness, and for its 

 numerous divisions into minute branches, which anasto- 

 mose together, and form an exceedingly delicate nervous 

 membrane, having, according to some, the papillary form 

 of termination. 



The Vidian nerve bestows common sensibility, and coming 

 from Meckel's ganglion belongs to the second division of the 

 fifth. Entering the hiatus Fallopii, it joins the portio dura 

 of the seventh in the aqueduct of Fallopius, and after a short 

 distance, leaves it to enter the tympanum, and through a 

 small foramen posterior to the pyramid. In this cavity it 

 is called chorda tympani, and sends branches to the tym- 

 panic plexus ; passes between the handle of the malleus and 

 long leg of the incus, and escapes at the fissure of Glasser. 



The portio-dura is a motor nerve and supplies the mus- 

 cles of the tympanum with their power of motion. 



The tympanic plexus seems to be the great source from 

 whence all parts of the tympanum are supplied, as it is 

 formed of branches from the chorda tympani, portio dura, 

 glosso pharyngeal, par vagum, and sympathetic; supply- 

 ing the membrana tympani, and lining membrane of the 

 cavity, the fenestra ovalis, the Eustachian tube, the muscles, 

 &c., and establishing relations with the soft palate, tongue, 

 pharynx, eye, nose, and system generally. 



Blood-vessels of the Ear. The arteries of the labyrinth 

 come from the internal auditory, which is a branch either of 

 the superior cerebellar or the basilar. This enters the mea- 

 tus along with the auditory nerve, pursues a similar course 

 and divides into minute branches, supplying the vestibule, 

 cochlea, and semi-circular canals. 



