ANTERIOR AREA. 45 



Lateral area. The lateral column of the spinal cord appears, on the surface, to 

 be directly continued upwards into the lateral area of the medulla oblongata. In 

 reality, however, a considerable tract of the white fibres that which in the spinal 

 cord we have noticed as the lateral pyramidal tract is found, at the upper end of 

 the spinal cord, to cross obliquely in stout bundles through the grey matter of 

 the anterior horn, and across the anterior median fissure to the other side of the bulb, 

 where it forms the mesial and larger part of the pyramid (figs. 36, 37). The rest of 

 the lateral. column can be traced vertically upwards (with the exception of the dorso- 

 lateral cerebellar tract which passes backwards into the restiform body) as far as the 

 lower end of the olive where its longitudinally coursing fibres become concealed by 

 this prominence and by the arched fibres already noticed. 



The olivary body or lower olive (figs. 32, 34, 36, o) is, as its name implies, an 

 olive-shaped prominence, which lies in the upper part of the bulb, immediately above 

 the apparent termination of the lateral column, and extending nearly as far as the 

 lower border of the pons, being only separated from this by a deep groove in which 

 is sometimes a small band of arched fibres. The line of exit of the hypoglossal 

 nerve-roots lies on its inner or mesial border, that of the accessory, vagus and glosso- 

 pharyngeal roots along its outer side, but the latter are separated from it by a groove 

 in which longitudinal fibres prolonged from the ventro-lateral cerebellar tract can be 

 seen. Sometimes there is a small longitudinal tract running along its inner border 

 also, and in such case, with the arched fibres above and below, the olive appears to 

 be entirely enclosed by a fibrous strand, which has sometimes been described as its 

 capsule (siliqua olivcn). This name is, however, more applicable to a layer of fibres 

 which immediately surrounds the dentate nucleus of the olive (see note on p. 56, 

 and fig. 44, s.o.). The longitudinal tracts on either side of the olive are often con- 

 cealed in great measure by the arched fibres, which may form a complete superficial 

 layer over the olive, and indeed over the whole anterior and lateral surface of this 

 upper part of the medulla oblongata. 



Anterior area. The anterior columns of the cord, although on superficial 

 inspection they appear to be prolonged into the pyramids of the bulb, are so 



Fig. 37. SECTION OP THE MEDULLA OBLONGATA AT THE MIDDLE OF 

 THE DECUSSATION OF THE PYRAMIDS. (Jjockharb Clarke.) 



/, anterior; f.p. , posterior fissure ; a.p., pyramid ; a, remains 

 of part of anterior cornu, separated by the crossing bundles from 

 the rest of the grey matter ; I, continuation of lateral column of 

 cord; R, continuation of substantia gelatinosa of Rolando; p. c., 

 continuation of posterior cornu of grey matter ; f.g., funiculus 

 gracilis. 



only to a small extent. For the lateral pyramidal 



bundles, crossing the anterior median fissure from the 



lateral column, are continued upwards close to that 



fissure, and unite with the comparatively small anterior 



pyramidal bundle to constitute the prominence known 



as the pyramid (anterior pyramid). The prolongation 



upwards of the rest of the anterior column of the cord lies deeply, being altogether 



concealed from view by the pyramids. 



The pyramids (figs. 30, a, 32, pa), are more prominent above than below. 

 They are bounded mesially by the anterior median fissure, and laterally by the 

 olivary bodies, being separated from these by the groove before mentioned, from 

 which the roots of the hypoglossal nerve issue. At their upper end they are 

 constricted, and become more completely separated from the rest of the medulla 

 oblongata. They are here very frequently crossed by a band of arched fibres, the 



