610 FUNCTIONS OF THE CEREBKO-SPINAL NERVOUS SYSTEM. 



G, constituting the vaso-motor centre, 1 and termed the antero-lateral nucleus. 

 These are connected together by a network in the lateral column, and by 

 nerve-fibres from the Tubercle of Rolando. The whole central part of the 

 gray substance of the Medulla is shown to be composed of commissural 

 bundles constituting the deep system of arciform fibres described by Lock- 

 hart Clarke. The decussation of the anterior pyramids is here much dimin- 

 ished ; for the fibres they derive from the lateral columns, which at first were 



FIG. 219. 



FIG. 218. Section through lower part of Olivary body. 

 FIG. 219. Section through poiut of Calamus Scriptorius. 



their principal source, have become comparatively few ; whilst those that 

 proceed from the posterior columns and central gray substance have been 

 gradually increasing in number, though not in a corresponding proportion. 

 The section shown in Fig. 219 is carried through the Medulla just at the 

 poiut of the Calamus Scriptorius, and shows that the hypoglossal ganglia 

 have retreated somewhat backward, pushing the mass of ganglionic cells 

 from which the spinal accessory arose, but which now constitute the origin 

 of the Pnewno gastric Nerves (v), to some extent outwards.' 2 The posterior 

 pyramidal (b) and restiform ganglia (a) have increased in size, and by 

 their lateral expansion form nearly one continuous mass on each side of the 

 Medulla, which, from the close interlacement of their fibres, presents a 

 spongy appearance, numerous cells being contained in the interstices. In 

 a recent paper read before the Royal Society, Mr. Lockhart Clarke 3 has 

 made one or two additions to the foregoing statement which may be here 

 noticed and will be understood from an examination of Fig. 220. It will 

 there be seen that between the hypoglossal and spinal accessory nuclei, the 

 cells of which are intimately connected together by communicating pro- 

 cesses, a small group of cells exist (7A), forming the attenuated point of a 

 fusiform tract which, augmenting as it ascends, insinuates itself between 

 the hypoglossal and the spinal accessory, now become the vagal nucleus ( r. ), 

 and that still higher (<:) it has attained a large size and forms in conjunc- 

 tion with another small vesicular tract, also situated to the inner side of the 

 hypoglossal nerve, the fasciculus teres, which lies on either side of the median 

 line. This tract constitutes the nucleus of the seventh. Intimately con- 

 nected with the nucleus of the seventh and with that of the glosso-pharyn- 

 geal by means of long fibres are the cells which form the motor tract of the 

 fifth, and which may be traced below the level of the middle of the olivary 

 bodies. The section displayed in Fig. 221 is carried through the upper part 



1 Ditttiiar. Lmhvig's Arhc>itcn fiir 1873, p. 11;"). 



; Thi- vesicular column which skives origin to the fibres of the spinal accessory, be- 

 comes t lie centre for t he Vagus about the level of the middle of the olivary bodies. 

 3 Phil. Trans., 1SHS, pt. f,~ p. 283. 



