CoGHiLL, Cranial Nerves of Amblystorna. 219 



into its ganglion. The neurones of the dorsal auditory root 

 form the r. acusticus sacculi; those of the ventral auditory root, 

 the r. acusticus utriculi. The peripheral relations of these rami 

 have been fully described by Herrick ('94) and need no farther 

 notice in this paper. 



The communis root of the facialis turns from its exit im- 

 mediately cephalad, mesially of the dorsal VIII root, ventrally 

 of the lateralis VII root and dorsal of the ventral VIII root. 

 As the latter root inclines laterad the communis root comes to 

 lie mesially of it, and in contact ventrally with the motor root 

 of the facial. As the communis root turns laterad into the 

 foramen it lies mesially and anteriorly of the motor VII. The 

 position of the geniculate ganglion, from which the axones of 

 the communis root arise, has been described on page 215. 



5. — The Motor Root of the Facialis. 

 The motor root of the facial nerve issues from the medulla 

 alone, ventrally of the anterior portion of exit of the auditory 

 roots. It becomes at once applied to the ventral surface of the 

 ventral VIII root, near the medulla. It holds this relative 

 position until the ventral VIII root turns laterad, when it meets 

 the communis root mesially of the ventral VIII root. It later 

 comes to He laterally and posteriorly of the communis root and 

 ventrally of the lateralis root. It crosses the postero-lateral 

 portion of the geniculate ganglion to enter the hyomandibular 

 trunk, and continues laterad in this trunk ventrally of the later- 

 alis root and its ganglion and dorsally of the communis compon- 

 ent of the trunk. 



B. THE RAMI OF THE TRIGEMINAL AND FACIAL NERVES, 



/. — The Ramus OpJuhalmiais Profundus V. 

 The general course of the r. ophthalmicus profundus is 

 cephalad and a little laterad from its ganglion, dorsally of the 

 proximal portion of the m. retractor bulbi and mesially of the 

 distal portion. It passes dorsally, also, of the m. rectus infe- 

 rior and m. rectus internus and of the optic nerve, and ventrally 

 of the m. rectus superior. In the region of the optic nerve the 

 ophthalmic divides into three terminal branches. 



