656 



THE SUBDIVISIONS OF THE MEDULLA OBLONGATA. 



rOf the fibres of the lateral column of the cord, some, the direct cerebellar tract, pass back- 

 wards to join the restiform body and go to the cerebellum. These fibres he as a thin layer on 

 the surface of the restiform body. The crossed pyramidal fibres cross obliquely, at the lower 

 end of the medulla, to the anterior pyramid of the opposite side and in their course they 

 traverse the grey matter of the anterior cornu (fig. 464, py). These fibres form the larger and 

 mesial portion of the anterior pyramid. The remaining fibres of the lateral columns are con- 

 tinued upwards, and pass beneath the olivary body, where they are concealed by this structure 

 and also by the arcuate fibres, but they appear in the floor of the medulla oblongata and are 

 here known as the fasciculus teres, which goes to the cerebrum. As they pass upwards, they 

 help to form the lateral part of the formatio reticularis.] 



[The posterior pyramid of the oblongata is merely the upward continuation ot the postero- 

 median column, or funiculus gracilis of the cord. As it passes upwards at the medulla it broadens 



fn 



Fig. 464 

 Section of the decussation of the pyramids, fla, anterior median fissure, displaced laterally by 

 the fibres decussating at d ; V, anterior column ; Ca, anterior cornu, with its nerve-cells, 

 a, b ; cc, central caual ; S, lateral column ; fr, formatio reticularis ; ce, neck, and g, head 

 of the posterior cornu ; rpCl, posterior root of the 1st cervical nerve ; nc, first indication 

 of the nucleus of the funiculus cuneatus ; ng, nucleus (clava) of the funiculus gracilis ; IP, 

 funiculus gracilis ; 2P, funiculus cuneatus ; sip, posterior median fissure ; x, groups of 

 ganglionic cells in the base of the posterior cornu. x 6. 



out, forming the clava, which tapers away above. The clava contains a mass of grey matter 

 the clavate nucleus.] 



[The restiform body consists chiefly of the upward continuation of the postero-external column 

 or funiculus cuneatus of the cord. It contains a mass of grey matter, called the cuneate or 

 triangular nucleus. Above the level of the clava, the funiculus cuneatus forms part of the 

 lateral boundary of the 4th ventricle. Immediately outside this, i.e., between it and the con- 

 tinuation of the posterior nerve-roots, is a longitudinal prominence, which Schwalbe has called 

 the funiculus of Bolando. It is formed by the head of the posterior cornu of grey matter 

 coming nearer the surface. It also forms part of the restiform body. Some arcuate fibres issue 

 from the anterior median fissure, turn transversely outwards over the anterior pyramids and 

 olivary body, and pass along with the funiculus cuneatus, the funiculus of Rolando, and the 

 direct cerebellar fibres, to enter the corresponding lateral lobe of the cerebellum, all these 

 structures forming its inferior peduncle. Some observers suggest that the funiculus cuneatus 

 and funiculus of Rolando do not pass into the cerebellum.] 



[The olivary body forms a well-marked oval or olive-shaped body, which does not extend 

 the whole length of the medulla (fig. 466, o). Above, it is separated from the pons by a groove 

 from which the 6th nerve emerges. In the groove between it and the anterior pyramid arise 



