MEDULLA OBLONOATA AND PONS VAROLII. 83 



The SEVENTH NERVE consists of two trunks, the FACIAL 

 and the AUDITORY. The facial is the smaller of the two and 

 most internal. It arises from the medulla oblongata, be- 

 tween the olivary and restiform bodies, close to the pons 

 Varolii. The auditory trunk arises by distinct filaments 

 from the floor of the fourth ventricle. A small bundle of 

 nervous filaments lies between these two nerves, and is 

 called the intermediate portion of Wrisberg ; it unites with 

 the facial nerve. 



The EIGHTH NERVE consists of three trunks, the GLOSSO- 

 PHARYNGEAL, the PNEUMOGASTRic, and the SPINAL ACCES- 

 SORY ; they are all situated along the side of the medulla 

 oblongata. 



The glosso-pharyngeal nerve is the smallest of the three, 

 and arises by three or more filaments, springing from the 

 restiform body, close to the facial nerve. 



The pneumogastric, or par vagum nerve, arises bel<fw 

 the preceding, also from the restiform body, by a series 

 of filaments which are finally gathered into a flat band. 



The spinal accessory nerve consists of two parts, one 

 being accessory to the pneumogastric and the other spinal. 

 The accessory part arises from the spinal cord by a series 

 of minute filaments in a line with the pneumogastric, ex- 

 tending as low as the first cervical nerve; this portion does 

 not unite with the pneumogastric nerve until it gets outside 

 the skull. The spinal part is a round cord arising by fila- 

 ments from the spinal cord, as low down as the sixth 

 cervical nerve. The glosso-pharyngeal, pneumogastric, and 

 spinal accessory nerves converge and meet just below the 

 crus cerebelli. 



The NINTH, or HYPOGLOSSAL NERVE, arises by a series 

 of filaments from the sulcus, between the pyramidal and 

 olivary bodies of the medulla oblongata, in a line with the 

 anterior roots of the spinal nerves. 



MEDULLA OBLONGATA AND PONS ^AROLII. 



The MEDULLA^BLONGATA is the upper enlarged portion 

 of the spinal cord. Its shape is pyramidal and its length 

 is about an inch and a quarter ; its base is limited by the 

 transverse fibres of the pons Yarolii, but its apex blends 

 with the cord and is not as definitely marked. The anterior 

 surface is convex, the posterior is somewhat concave an'd 

 forms the floor of the fourth ventricle. It is divided into 

 halves by a median longitudinal fissure in front and behind, 



