THE STRUCTURE OF THE BRAIN STEM 427 



(3) Splanchnic Motor Nuclei. These lie more deeply at some 

 distance from the middle line, and include the nucleus ambiguus for 

 the efferent fibres of the vago-glossopharyngeal, the nucleus of the 

 seventh or facial nerve (originally splanchnic or branchial, now 



.MIDDLE 

 PEDUNCLE 



OF 

 CEREBELLUM 



FIG. 193. Diagram showing the brain connections of the vagus, glosso- 

 pharyngeal, auditory, facial, abducent, and trigeininal nerves. (CUN- 

 NINGHAM after OBERSTBINER.) 



typically somatic), and the motor nucleus of the fifth nerve with its 

 prolongation into the mid-brain. 



(4) Sensory Somatic Nuclei. The chief representative of this group 

 is the great sensory root of the fifth nerve. The fibres of this nerve 

 arise from the Gasserian ganglion, pierce the fibres of the pons Varolii, 

 and run to the dorso-lateral part of the pons, where they divide into 

 ascending and descending fibres. These fibres form a cap to the 

 substantia gelatinosa, the descending branches, which are longer, 

 being conspicuous in sections of the medulla as low down as the first 



