44 



THE MEDULLA OBLONGATA AND PONS VAROLII. 



ventricle in its lower part. Above, the clavse are tapered off and soon become no 

 longer traceable. 



The funiculi graciles with their clavas are sometimes described as foa posterior, pyramid*. 



Between the postero-mesial column and the postero-lateral groove from which 

 the posterior roots of the cervical nerves pass out there is found in the upper part of 

 the cord a single distinct column, viz., the postero-lateral column (tract of Burdach). 

 This is also prolonged into the medulla, and also like the funiculus gracilis expands 

 as it is traced upwards : it is here known as the funiculus cuneatus. Outside this 

 funiculus cuneatus and between it and the line of roots of the spinal accessory 

 another longitudinal prominence is caused by the fact that the substantia gelatinosa 

 of Rolando begins near the lower end of the bulb to project towards the surface 

 as a distinct funiculus, narrow below but broadening as it is traced upwards, where it 

 forms a considerable eminence known as the tubercle of Rolando. The longitudinal 

 prominence which passes up into it, is termed therefore by Schwalbe, the funiculus 

 of Rolando (bg. 35, /.#.). 



The funiculus of Rolando is termed by Henle the lateral cuneate funiculus. 



On a level with the adjoining clava of the funiculus gracilis, the enlarged part of the 

 cuneate funiculus also, like that, exhibits a slight eminence, which is best marked in children, 

 and has been termed the cuneate tubercle (Schwalbe). 



In the upper part of the medulla oblongata, the cuneate funiculus is concealed by 

 a set of fibres (external arched or arcuate fibres) which issue from the anterior median 



Fig. 36. DISSECTION OP THE MEDULLA OBLONGATA AND PONS 



SHOWING THE COURSE OF THE PTRAMIDAL TRACTS IN THEM. 



(Allen Thomson.) 



P, pons Varolii ; p, the pyramids, the upper part of the 

 right one has been cut away ; p', the fibres of the left 

 pyramid, as they ascend through the pons, exposed by the 

 removal of the superficial transverse fibres ; p" is placed on 

 some deeper transverse fibres of the pons on the right side, 

 below the divided fibres of the right pyramid ; a, left 

 anterior column of the cord, its median part passes upwards 

 into the outer part of the pyramid, the remainder dips 

 beneath the pyramid and olivary body ; o. olivary body ; o', 

 the continuation of part of the lateral column ascending 

 through the pons and exposed by the removal of a small 

 portion of the deeper transverse fibres ; o", some of the 

 same fibres divided by a deeper incision on the right side ; 

 I, I', the lateral columns of the cord ; x , their deeper parts 

 passing by decussation into the pyramids ; r, direct cere- 

 bellar tract passing from the lateral column into the inferior 

 peduncle of the cerebellum, or restiform body ; r', fasciculus 

 passing from the anterior column to the same ; ft, deep 

 longitudinal fibres derived from the anterior and lateral 

 columns of the cord. 



B, explanatory outline of the section of the spinal cord, 

 a, anterior columns ; p, posterior ; I, lateral. 



fissure and passing laterally over the surface of the pyramid and olive, turn upwards 

 to join the restiform body. There is also a narrow strand of fibres from the lateral 

 column of the cord, marked by its white appearance, which joins this tract of oblique 

 fibres just above the level of the tubercle of Rolando. This is the dor so-lateral (direct) 

 cerebellar tract which has been already noticed in the description of the spinal cord. 

 These obliquely crossing fibres turn upwards as they cross the funiculus of Rolando, 

 and appear to blend with that column and with the cuneate funiculus. They do 

 not, however, actually blend with them, but are reinforced by a large number of fibres 

 coming from the opposite side of the bulb (see p. 52, fig. 44), and the whole mass 

 of fibres thus produced forms a rounded, prominent cord, the corpus restiforme, or 

 rope-like body (fig. 36, r), which passes directly into the corresponding hemisphere 

 of the cerebellum, constituting its inferior peduncle. 



