SURFACES. 287 



inferior end of the pons in a blind foramen (foramen caecum of 

 Vicq d'Azyr). On either side of the median fissure, the ante- 

 rior surface presents a fusiform eminence, most prominent near 

 the pons, called the pyramid. The pyramidal tract, which we 

 have already traced through the internal capsule, basis pedunculi 

 and pons, forms tEe pyramid of the medulla. In the lower part 

 of the medulla the pyramid divides into two tracts, viz., the lateral 

 (or crossed) pyramidal tract and the anterior (or direct) pyrami- 

 dal tract, the former comprising about the medial four-fifths and 

 the anterior pyramidal tract the lateral one-fifth of the pyramid. 

 Transverse fibers, called the anterior external arcuate, are also 

 seen crossing the pyramid from within outward. They form a 

 more or less continuous sheet of fibers, which emerges from the 

 anterior median fissure and winds around the medulla to the 

 posterior 'surface, where its fibers enter the restiform body. The 

 anterior surface is identical with the surface of the two anterior 

 areas of the medulla. 



Lateral Surface. (Fades lateralis, Figs. 81 and 85). There 

 are two lateral surfaces, a right and a left. Each is bounded by 

 the anterior lateral and the posterior lateral sulcus; and is inclosed 

 between the roots of the hypoglossal nerve, ventrally, and those 

 of the ninth, tenth and the cerebral portion of the eleventh, dor- 

 sally. Lateral surface is synonymous with the surface of the lat- 

 eral area. The lateral surface is formed, above, by the olive, below, 

 by the lateral column and, winding backward over both, are the 

 anterior external arcuate fibers. 



The olive (oliva) is an elongated eminence, a half inch in 

 length, situated just below the pons (Fig. 85). It is produced 

 by the inferior olivary nucleus in the lateral area of the medulla; 

 and, superficially, is composed of fibers continuous with the fascic- 

 ulus proprius of the lateral column in the spinal cord (Fig. 93). 



Lateral Column. (Funiculus lateralis, Fig. 85). It is made 

 up of three great bundles of fibers (Figs. 93, 94 and 95): The 

 lateral fasciculus proprius, which, splitting into a superficial and 

 a deep lamina, incloses the inferior olivary nucleus; the anterior 

 descending cerebello-spinal tract, running down the anterior lateral 

 sulcus; and the anterior ascending cerebello-spinal and spino- 



