340 NERVOUS SYSTEM. 



principal destination is to the abductor, among the fleshy fas- 

 ciculi of which its ramifications are pretty equally distributed. 



Seventh Pair, or Auditory. 



This pair includes two separate nerves on either side : one, 

 from its remarkable softness, is denominated the portio mollis; 

 the other, in contradistinction, the portio dura. 



THE PORTIO MOLLIS takes its rise from the floor of the 

 fourth ventricle, by the side of the crena of the calamus scrip- 

 tori us. It turns round the medulla oblongata, and- then passes 

 directly outward, and enters the foramen auditorium internum. 

 Having gained admission into the vestibule of the internal ear, it 

 resolves itself into divers pulpy filaments, which pierce a per- 

 forated bony plate, and ramify over the various parts of the la- 

 byrinth. 



THE PORTIO DURA arises from the place of union of the 

 medulla oblongata, tuber annulare, and crus cerebelli ; and takes 

 its passage through the foramen auditorium internum, inclosed in 

 the same sheath of dura mater along with the portio mollis. At 

 the bottom of the meatus auditorius internus, it detaches two 

 slender but important branches. 1. The chorda ti/mpaui, a long 

 slender filament which proceeds into the cavity of the tympanum, 

 crosses therein the neck of the malleus, makes its exit again by 

 a small foramen, and, descending to the root of the tongue, 

 forms a remarkable union with the lingual nerve. 2. The other 

 also runs in the vicinity of the tympanum, but subsequently 

 pursues the course of the Eustachian tube : deeply seated within 

 the fauces at its exit, its branches become distributed over the 

 parts in the immediate vicinity. 



The portio dura leaves the internal ear through the spiral 

 canal, and is deeply buried at its issue underneath the parotid 

 gland, giving off there the auricular nerves, of which there are 

 three principal divisions. 1. The anterior auricular nerve ascends 

 over the fleshy root of the front of the ear, where it detaches 

 some branches which unite with others coming from the lachry- 

 mal branch of the first division of the fifth pair, and form a 

 sort of plexus — the anterior auricular plexus. Its remaining 

 branches are dispersed upon the skin thereabouts. 2. The pos- 

 terior auricular nerve, less in size, mounts the back of the ear, 

 in company with the bloodvessels, distributing branches to the 

 muscle about its root, and vanishing in ramifications upon the 

 skin of the ear. 8. The internal auricular, the least considerable 

 of the three, enters the concha for the supply of the parts contained 

 in the external ear. 4. Parotideal branches, two, three, or four 

 in number, ramifying within the substance of the gland, and 



