634 STRUCTURE OF THE BULB, PONS, & MID-BRAIN. [CH. XLIV. 



the other side, become a longitudinal bundle, which lies just dorsal 

 to the pyramid (py], and passes upwards to various parts of the 

 cerebrum, passing, however, through one or more cell stations 

 (positions of relay) before ultimately arriving at the cortex. 



We now see that the brain has a crossed relationship to the body, 

 the left half of the brain governing the right half of the body, 



Fig. 468. Section of the medulla oblongata at about the middle of the olivary body. 

 f.l.a., anterior median fissure ; n.ar., nucleus arcuatus ; p, pyramid ; XII., bundle 

 of hyppglossal nerve emerging from the surface ; at b, it is seen coursing between the 

 pyramid and the olivary nucleus, o ; f.a.e., external arcuate fibres ; n.l., nucleus 

 lateralis ; a., arcuate fibres passing towards restiform body, partly through the sub- 

 stantia gelatinosa, g., partly superficial to the ascending root of the fifth nerve, a. V. ; 

 X., bundle of vagus root emerging ; f.r., formatio reticularis ; C.r., corpus restiforme, 

 beginning to be formed, chiefly by arcuate fibres ; superficial and deep ; n.c., nucleus 

 cuneatus ; n.g., nucleus gracilis ; t. attachment of the ligula ; f.s., funieulus solitarius ; 

 n.X., n.X.', two parts of the vagus nucleus ; n.XII., hypoglossal nucleus ; n.t., nucleus 

 of the funieulus teres ; n.am., nucleus ambiguus ; r., raph<5 ; A., continuation of the 

 anterior column of cord ; o', o", accessory olivary nucleus ; p.o.l., pedunculus olivee. 

 (Modified from Schwalbe.) 



and vice versa, both as regards motion and sensation ; the motor 

 fibres mostly cross at the decussation of the pyramids, some few 

 (those in the direct pyramidal tract) crossing at lower levels in 

 the cord ; the sensory fibres mostly cross at the decussation of 

 the fillet, though some few cross at lower levels in the cord, soon 

 after their entrance into the cord by the posterior nerve-roots. 



Other points to be noticed in the section are the substantia 

 gelatinosa of Rolando (g) (remains of posterior cornu of the cord), 

 now separated from the surface by the ascending root of the fifth 



