ANATOMY OF THE MEDULLA OBLONGATA 121 



medial longitudinal fasciculus, which is continuous with the anterior fasciculus 

 proprius of the spinal cord. 



The lateral area of the medulla oblongata, included between the antero- 

 lateral and posterolateral sulci, appears as a direct continuation of the lateral 

 funiculus of the spinal cord; but, as a matter of fact, many of the fibers of that 

 funiculus find their way into the anterior area (as, for example, the lateral cor- 

 ticospinal tract) or into the posterior area (dorsal spinocerebellar tract). In 

 the rostral part of the lateral area, between the root filaments of the glosso- 

 pharyngeal and vagus nerves, on the one hand, and those of the hypoglossal, 

 on the other, is an oval eminence, the olive (oliva, olivary body), which is pro- 

 duced by a large irregular mass of gray substance, the inferior olivary nucleus, 

 located just beneath the surface (Figs. 87, 88). By a careful inspection of the 

 surface of the medulla oblongata it is possible to distinguish numerous fine 

 bundles of fibers, which emerge from the anterior median fissure or from the 

 groove between the pyramid and the olive and run dorsally upon the surface 

 of the medulla to enter the restiform bodies. These are the ventral external 

 arcuate fibers and are most conspicuous on the surface of the olive (Fig. 88) . 



In the sheep there are two superficial bands of fibers not seen in the human 

 brain. Placed transversely near the caudal border of the pons is a belt-like 

 elevation, known as the trapezoid body, through which emerge the roots of the 

 abducens and facial nerves (Figs. 83, 87). In man the much larger pons covers 

 this band from view and the sixth and seventh nerves emerge from under the 

 caudal border of the pons. Another bundle, beginning on the ventral sur- 

 face of the trapezoid body near the seventh nerve, describes a graceful curve 

 around the ventral border of the olive and becomes lost in the lateral area of 

 the medulla oblongata. This has been called the fasciculus lateralis minor. 



The dorsal area of the medulla oblongata is bounded ventrally by the pos- 

 terolateral sulcus and emergent root filaments of the glossopharyngeal, vagus, 

 and accessory nerves. In the closed part of the medulla oblongata it extends 

 to the posterior median fissure, while in the open part its dorsal boundary is 

 formed by the lateral margin of the floor of the fourth ventricle. The caudal 

 portion of this area is, in reality, as it appears, the direct continuation of the 

 posterior funiculus of the spinal cord. On the dorsal aspect of the medulla 

 oblongata the fasciculus cuneatus and fasciculus gracilis of the cord are con- 

 tinued as the funiculus cuneatus and funiculus gracilis, which soon enlarge into 

 elongated .eminences, known respectively as the cuneate tubercle and the clava 

 (Figs. 89, 91). These enlargements are produced by gray masses, the nucleus 



