STRUCTURE OF THE MEDULLA OBLONGATA. 



Gil 



of the Medulla Oblongata, and shows the Glosso-pharyngeal arising at a 

 higher level, but from the same series of ganglionic cells as those from 

 which the Spinal Accessory and Pneumogastric roots have successively 

 arisen, and which are now sunk beneath two new masses of vesicular sub- 



FIG. 221. 



.\lult 



FIG. 220. Diagram showing the position of the Nuclei in the Medulla Oblongata: a, at the end of 

 the lower third of the olivary body ; 6, at the middle of the olivary body ; c, at the upper extremity of 

 the olivary body ; H, Hypoglossal ; s A, Spinal Accessory ; v, Vagus ; 7, Portio dura ; 5, Motor root of 

 the fifth. 



FIG. 221. Section through upper part of the Medulla Oblongata. 



stance from which the Auditory nerves take their origin. The Auditory 

 nerve itself is seen to divide into two portions, one curving round the side 

 of the Medulla, and forming the well-known transverse elevation on the 

 floor of the Fourth Ventricle, to terminate in the inner or posterior audi- 

 tory nucleus and to some extent in the outer nucleus, the other dipping into 

 the substance of the cord in front of the Restiform body to reach the outer 

 nucleus formed by the summit of the posterior pyramid and apparently by 



FIG. 223. 



Su/i'ffd afCtrtltU. 



FIG. 222. Longitudinal section of the Medulla Oblongata: o, pyriform gray substance of the resti- 

 form and post-pyramidal bodies ; p, superficial gray substance of the restiform body ; 6, posterior pyra- 

 mid ; 6', its gray substance; g, vagal nucleus; I, spinal accessory nucleus; n, slender column partic- 

 ularly connected with the glosso-pharyngeal and with the vagal and spinal accessory roots of origin. 



FIG. 223. Section made through the summit of the Medulla Oblongata. 



part of the nucleus of the Pneumogastric nerve. The gangliouic cells which 

 give origin to the motor root of the fifth nerve are here very apparent. If 

 the parts just described are examined in longitudinal section the appear- 

 ances are those shown in Fig. 222, and are thus described by Mr. Lock- 

 hart Clarke. 1 If the posterior pyramid b, b' (on the left side) be carefully 



i Researches on the Intimate Structure of the Brain. Second Series. Phil. Trans. 

 Part i, 18U8, p. 267. 



