612 FUNCTIONS OF THE CEREBRO -SPINAL NERVOUS SYSTEM. 



dissected from the restiform body from below upwards, and be thrown for- 

 wards, the tract will be exposed from which the spinal accessory and pneu- 

 mogastric nerves arise. The part indicated by t is the nucleus of the spinal 

 accessory nerve. The oval mass, g, marked off by the dotted line, is the 

 inner and posterior portion of the vagal nucleus. Continuous with the pre- 

 ceding, and exposed at the point of the calamus scriptorius by the divergence 

 of the posterior pyramid, I, is its inner and more anterior portion, covered 

 like the spinal accessory nucleus, t, lower down, by the posterior pyramid, 

 as seen in Figs. 218 and 219. Its upper point, m, forms the principal nu- 

 cleus of the glosso-pharyngeal nerve. Along the outer and anterior part of 

 this gray tract is a slender longitudinal white column, which is lodged as it 

 were in a groove, and which tapers to a point as it descends obliquely inwards 

 along the base of the posterior pyramid to the mesial line. In its upward 

 course it lies along the inner edge of the pyramid, and joins those fibres of 

 the latter which pass into the anterior or outer auditory nucleus. On the 

 outer side of this slender white column is a somewhat fusiform mass of gray 

 substance (0} imbedded in the inner side of the restiform body, and exposed 

 by the removal of the posterior pyramid. From the upper extremity of 

 this mass a thin but broad layer of fibres, mixed with some gray substance 

 (p), radiates upward and outward on the restiform body. The deep origins 

 of the fifth, sixth, and Portio Dura of the seventh, are further shown in the 

 section Fig. 213. The sixth and Portio Dura seem to form almost a loop, 

 and to be continuous with each other through a common gangliouic centre 

 from whence they arise, situated above but in the same line with that of the 

 hypoglossal, and both may be traced to the superficial gray layer of the fas- 

 ciculus teres, but each of these nerves has besides a separate nucleus of its 

 own. When the portio dura of the seventh nerve reaches the fasciculus 

 teres, as shown in Figs. 228, 225, it runs longitudinally down the medulla, 

 and after a very short course again bends transversely forward to form a 

 loop along the side of the median furrow. The summit of this curve consti- 



loop 



arm of the loop in its course forwards divides like a brush into separate 

 fibres, which plunge into the motor nucleus of the fifth nerve, and into the 

 superior olivary body, or gray nucleus of the trapezium. As regards the 

 sixth, the lower fibres arise from the ganglion common to it and the portio 

 dura of the seventh, and also from the gray matter of the fasciculus teres, 

 whilst the upper fibres arise from the upper and inner part of the common 

 ganglion, which may here be regarded as a separate centre or nucleus, as the 

 outer portion from which the portio dura previously arose, has become much 

 attenuated, and ceases to give origin to the fibres of that nerve. The close 

 relation which exists between the nuclei of origin of the hypoglossal, glosso- 

 pharyngeal, spinal accessory, vagus, facial, and trigeminal nerves, is of much 

 interest, and serves to explain certain symptoms accompanying various forms 

 of paralysis, in which the muscles concerned in deglutition, vocalization, 

 articulation, and expression are affected. The motor and sensory roots of 

 the fifth arc separated from one another at their origin by the Portio Dura. 

 The connection of the motor root with the glosso-pharyngeal nucleus and 

 with the fasciculus teres or nucleus of the seventh, has already been noticed. 

 The Posterior or Sensory root runs down through the front of the gray 

 tubercle or caput cornu posterior, which may be regarded as the continua- 

 tion of its nucleus, and is in most intimate relation with the fibres of origin 

 of the vagus and glosso-pharyngeal nerves, which pass through this portion 

 of the fifth nerve. The origins of the fourth pair of Cerebral nerves have 



