516 



THE MEDULLA OBLOXGATA. 



plicated, so as to give the indented appearance to a section. This capsule is, 

 moreover, surrounded with white matter externally, and through its open part 

 white fibres pass into or issue from its interior, and connect it with other 

 parts of the brain. The external fibres of the anterior columns of the cord, 

 which at the decussation of the pyramids are thrown outwards, are con- 

 tinued upwards, on the surface of the medulla oblongata, and then pass 

 partly on the outside of and partly beneath the olivary bodies being joined 

 in their further progress by the fibres issuing from the olivary nucleus. To 

 these fibres the term olivary fasciculus has been applied. 



The restiform bodies, placed behind and to the outer side of the olivary 

 bodies, are two lateral rounded eminences or columns directly continuous with 

 the posterior, and with part of the antero-lateral columns of the cord ; they 

 diverge slightly as they ascend, and thus occasion the greater width of the 



Fig. 350. Fig. 350. VIEW OF THE POSTERIOR SURFACE OF 



THE PONS VAROLII, CORPORA QUADRIGEMINA, 

 AND MEDULLA OBLONGATA. 



The peduncles of tbe cerebellum are cut short 

 at the side, a, a, the upper pair of corpora quadri- 

 gemina ; 6, b, the inferior ;/,/, superior peduncles 

 of the cerebellum ; c, eminence connected with 

 the nucleus of the hypoglossal nerve; e, that of 

 the glosso-pharyngeal nerve ; i, that of the vagus 

 nerve ; d, d, restiform bodies ; p, p, posterior 

 pyramids ; v, v, groove in the middle of the fourth 

 ventricle ; v, calamus scriptorius, and eminence 

 connected with the spinal accessory nerve ; 7, 7, 

 roots of the auditory nerves. (See also Fig. 357, 

 at p. 525.) 



medulla at its upper part. Each of them 

 passes into the corresponding hemisphere 

 of the cerebellum, and constitutes its 

 inferior peduncle. At first they are in 

 contact with the small tracts of the 

 medulla, named the posterior pyramids ; 

 but higher up they become free and pro- 

 minent, and assist in forming the lateral boundaries of the fourth ventricle. 

 There is a considerable portion of grey matter in their interior. 



By far the larger portion of the white substance of the restiform body 

 consists of longitudinal fibres, which include all those belonging to the 

 posterior column of the cord except the fasciculus gracilis, some derived 

 from the lateral column, and also a small band from the anterior column. 

 This last-named band runs obliquely below the olivary body, and, as was 

 shown by Solly, connects the anterior column with the cerebellum. 



The part of the posterior column of the cord which belongs to the resti- 

 form body of the medulla, is named fasciculus cuneatus. 



The posterior pyramids (fasciculi graciles) of the medulla oblongata, the 

 smallest of the four pairs of columns into which it is divided, are situated 

 one on each side of the posterior median fissure. They consist entirely of 

 white fibres, and are continuous with the posterior slender tracts of the 

 cord. They increase in size as they ascend till they reach the point where 

 the medulla opens out to form the floor of the fourth ventricle ; and there, 

 diverging from one another, they have the appearance of tapering and 

 become closely applied to the restiform bodies. Their fibres quit these 

 bodies, however, and pass up to the cerebrum. 



