MEDULLA OBLONGATA 527 



presence of two elongated nuclei, which lie subjacent to 

 them aftd gradually increase as they are traced upwards. 

 These are termed the gracile and the cuneate nuclei, and it 

 can easily be shown that as the grey matter increases in 

 quantity the fibres of the two corresponding strands diminish 

 in number. Indeed, it is doubtful if any of their fibres are 

 prolonged upwards beyond the level of the nuclei. 



But a third longitudinal elevation also is apparent in the 

 lower part of the posterior area of the medulla oblongata. This 

 is placed on the lateral side of the funiculus cuneatus between 

 it and the posterior row of nerve fila and it has no counter- 

 part in the posterior funiculus of the spinal medulla. It is 

 called the funiculus of Rolando, because it is produced by 

 the substantia gelatinosa Rolandi approaching the surface. 

 Extremely narrow below, the funiculus of Rolando widens 

 somewhat as it is traced upwards, and it, finally, ends in an 

 expanded extremity called the tubercle of Rolando. The thin 

 layer of fibres which appear on the surface of the tubercle 

 and funiculus of Rolando and cover the substantia gelatinosa 

 Rolandi in this positiori belong to the tractus spinalis (O.T. 

 spinal root) of the trigeminal nerve. 



The restiform body forms the upper part of the posterior 

 area on each side. It lies between the lower part of the 

 floor of the fourth ventricle and the fila of the vagus and 

 glosso-pharyngeal nerves, and is thrust laterally by the en- 

 largement of the fourth ventricle. It is a large rope-like 

 strand, which inclines upwards and laterally, and then finally 

 takes a turn posteriorly, and enters the cerebellum, of which 

 it constitutes the inferior peduncle. The restiform body, there- 

 fore, is to be regarded as the main connection between the 

 cerebellum, above, and the medulla oblongata and medulla 

 spinalis below. At the same time, it must be understood 

 that it is not formed of fibres which are prolonged into it 

 from the funiculus gracilis and funiculus cuneatus of its 

 own side. It is true that a surface inspection of the 

 medulla oblongata might lead very naturally to this supposi- 

 tion, because there is no sharp line marking it off from the 

 tubercles of these strands. 



The fibres which build up the restiform bodies come from several differ- 

 ent sources. It will be sufficient to indicate the more important of these 

 (i) from the lateral funiculus of the spinal medulla through the fasciculus 

 cerebellospinalis ; (2) from the cerebellum as the cerebello-olivary fibres 



