82 Journal of Comparative Neurology 



IX. Glosso-Pharyngcal Nerves. — This pair originates a short 

 distance caudad of the 8th nerve as slender trunks. These 

 trunks pass laterad and pierce the dura and skull directly. Their 

 course on first entering the skull is along the caudal margin of 

 the auditory capsule, in the cartilaginous walls of which they 

 lie imbedded. 



X. Vagus or Pneumogastric Nerves. — These arise as three 

 bundles of fine fibers along the lateral wall of the oblongata at 

 nearly the same level as the origin of the 9th pair. An appar- 

 ent individual variation exists in the number and arrangement of 

 the tiny fibers that go to make up these three bundles. These 

 bundles pass almost directly laterad and unite into a common 

 trunk as they enter the foramen. After a short course this 

 common trunk unites with that of the 1 ith and will be traced 

 under that pair. 



XI. Spinal Accessory Nerves. — Each nerve of this pair 

 originates by six roots (Figs. 1, 2). The most cephalic root 

 lies at the same level as the tenth, the caudal roots gradually 

 approach the dorsal margin, the most caudal lying far dorsad. 

 Another peculiarity in these roots is their wide cephalo-caudal 

 distribution, extending from near the middle length of the ob- 

 longata into *the myel beyond the first pair of cervical nerves. 

 These six roots form a common trunk that enters the same for- 

 amen as the tenth. These two trunks lie close together wrapped 

 in a common envelope of connective tissue, but do not unite 

 until they have passed some distance into the skull (in Fig. 2 they 

 are shown widely separated but in nature they are close to- 

 gether). Directly after their union they form a small ganglion. 

 A short distance peripherad of this ganglion they are joined by 

 the 1 2th nerve. 



XII. Hypoglossal Nerves. — Each nerve of this pair origin- 

 ates by three roots from near the ventral furrow ventrad of the 

 cephalic roots of the eleventh ( Fig. 2 ). I find a very notice- 

 able individual variation in the relative size of each bundle and 

 in the number of separate threads that go to make up each par- 

 ticular root. The two cephalic roots may unite before they 



