1881.] -'-^*^ [Stowell. 



given off 4-6 mm. cephalad of union of AA. vertebrales. These filaments 

 unite about 1 mm. peripherad of their superficial origin into six or seven 

 ramuli, which lie ventrad of plexus choroideus lateralis (Fig. 2, PI. Ch.), 

 and blend in foramen jugulare to form a single flattened nerve trunk, N. 

 vagus. In the passag'e through the foramen 6 mm. peripherad of 

 its origin, N. vagus is enclosed in common with N. accessorius (XI) in 

 a sheath formed by a tubular prolongation of the dura mater and the 

 arachnoid membrane, where it is also joined by N. glosso-pharyngeus 

 (IX) ; but the sheath of the united NN. vagus (X) and accessorius (XI) 

 maybe reaflily dissected from that of N. glosso-pharyngeus (IX), which lies 

 ectad and cephalad. Centrad of its foramen of exit — Foramen jugulare, 

 (Foramen lacerum-posterius, Lacerum foramen posterius) — and 3-4 mm. 

 peripherad of medulla oblongata, N. vagus presents a ganglionic enlarge- 

 ment, g-angiion jug-illare, ganglion of the root. This ganglion ishemi- 

 sphei'ical in form, of a grayish color, and measures nearly 2 mm. in diam- 

 eter ; it has relations with NN. facialis, glosso-pharyngeus, accessorius 

 and sympathicus (Fig. 5, J). 



At G. jugulare, N. vagus is connected by a single twig with the adjacent 

 petrous ganglion of N. glosso-pharyngeus (IX) the "ganglion of An- 

 dersch" (Fig. 5, Pe.); by a considerable trunk with N. accessorius (Fig. 

 6, 10);hj ramus auricularis (Fig. 5, 2), with N. facialis (VII), from which 

 ramus, a slender ramulus penetrates the petrous bone and joins a branch 

 of N. facialis; a portion of the ramus continues across N. facialis to the 

 cochlea (Fig. 5, 5), a filament from the auricular branch connects with a 

 ganglionic plexus of N. sympathicus, entad of the gangliform plexus of 

 N. vagus. 



Plexus gangliforniis. The 5 mm. of N. vagus immediately caudad 

 of G. jugulare is involved in a somewhat intricate net-work, which seems 

 to be allied to plexus gangliformis (Fig. 6., Px. gang.); the apposed trunks 

 of NK. glosso-pharyngeus (IX), vagus (X), accessorius (XI) and hypo- 

 glossus (XII), are embraced by interlacing filaments of N. sympathicus, 

 with which nerve they sustain more or less intimate relations, through 

 anastomotic filaments; N. glosso-pharyngeus is ectal in this group, and, 

 together with its root-ganglion — G. Ehrenritteri, which lies upon the ectal 

 surface of G. jugulare, but which does not seem to sustain anatomical re- 

 lations with it — may be dissected from the ental trunk; NIST. vagus and 

 accessorius are most intimately related — their separation involving the 

 rupture of interlacing fibre — and apparently constitute a single trunk; 

 entad of this united trunk is N. liypoglossus. At the caudal border *f this 

 plexus N. accessorius is directed dorsad to be distributed to the muscles of 

 the neck, and N. liypoglossus assumes ectal relations, crossing the ectal 

 surface of N. vagus nearly at right angles, and takes its course ventrad, to 

 the muscles of the tongue. As IST. hypoglossus crosses N. vagus, it de- 

 taches a filament to G. inferius (Fig. 5,. IS). This region marks the origins 

 of two other rami with whose terminal filaments N. vagus sustains inti- 

 mate relations, NN. thyro-hyoideus and descendens noni. 



