19 



Stowel!.] -■— ' [Nov. 5, 



the middle of the malleus, somewhat mesad of the bone, and emerges 

 through a minute foramen, the iter chordae anterius, into the glaserian 

 canal, thence along the canal to the ecto-cranial foramen ; it lies ventrad 

 of the otic ganglion and the dental branch of the mandibular nerve, eclad 

 of the external carotid artery, passes between the pterygoid muscles, and 

 joins the lingual nerve at an acute angle about 5-10 mm. peripherad of 

 the foramen ovale. 



Nervus petrosus superficialis major. — The great petrosal nerve has a 

 fourfold origin. Tiie principal root may be traced to the geniculate gan- 

 glion with the trunk which is directed caudad from that body ;* the next 

 in size comes direct from the petrosal ganglion of the glosso-pharyngeal 

 nerve, and is a division of Jacobson's nerve ; the third is a brancli from 

 the trunk of the facial, at the angle ; and the fourth is a slender filament 

 from the tympanic plexus (Jacobson's). The united trunk lies in the 

 glaserian canal, and emerges from its ventral hiatus, enters the caudal 

 foramen of the Vidian canal, which is about 5 ram. cephalad, traverses 

 the canal, and at the middle of the foramen lacerum anterius becomes the 

 petrosal root of the Vidian nerve, whence it is related to the spheno-pala- 

 tine ganglion. 



Nervus petrosus superficialis minor. — This branch from the inter- 

 osseous portion of the facial nerve is one of the four divisions of the ramu- 

 lus given off at the angle ; about 2 mm. peripherad of its origin it enters 

 an enlargement (plexus?) about .5 mm. in diameter; this enlargement is 

 ioined by the tensor tympani nerve ; the petrosal nerve traverses the 

 glaserian canal and joins the otic ganglion at the ventral hiatus. 



Ecto-cranial Relations. — The ecto-cranial trunk emerges from the 

 foramen stylo masloideum ; its course is cephalad and dorsad, and lies 

 ectad of the post-auricular artery. (It often lies entad of a branch artery 

 to the parotid gland.) At the foramen of exit, or just peripherad, the 

 nerve divides into branches; its relations and distribution are given ac- 

 cordingly. The primary rami ventrad are the digastric and the stylo- 

 hyoid ; cephalad are the cervico-facial and the tempore- facial ; dorsad and 

 caudad are the auricular. 



N. digastricus. — The digastric nerve is a small ramus from the ventral 

 border of the facial nerve at its foramen of exit ; it lies entad of the stylo- 

 mastoid artery, around the cephalic border of whicli it bends abruptly 

 and takes its course ventrad ; it extends along the dorsal border of the 

 proximal end of the digastric muscle, which it penetrates about 5-8 mm. 

 from its origin ; its terminal filaments supply the proximal end of the 

 muscle. (I do not find an anastomotic branch to the glosso-pharyngeal 

 nerves, as is the case in man.) 



N. stylo hyoideus arises from the ventral border of the facial nerve, 

 in common with the digastric, or remains in the truuk-sheath to be given 

 off about 1-3 mm. peripherad ; it penetrates the stylohyoid muscle at its 



*This trunk becomes the anastomotic branch to the glosso-pharyngeal and 

 the vagus uerves, the chorda tympani and the long root of the petrosal nerve. 



