630 



PHYSIOLOGY. 



their march forward and upward, travel through the base of the 

 anterior horns in the form of a multitude of small bundles. These 

 arch and decussate from side to side. 



Still higher up the fillet decapitates, as it were, the posterior 

 horns. The caput comes close to the surface, where it forms the 

 distinct projection known as the gelatinous substance of Eolarido. 

 The cervix of the cornu becomes broken up in a manner similar to 

 that of the anterior horn. 



White Substance of the Medulla. This is formed by the pro- 

 longation of the columns of the spinal cord and by additional white 

 masses, the olives and arcuate fibers. 



RA 



RP, 



RP 



R A 



NR 



Fig. 244. 



Section of Medulla Oblongata 

 at the Level of the Decussation of 

 the Pyramids Motor Decussation. 

 (M. DUVAL.) 



1, 2, 3, Anterior, lateral and posterior 

 columns. CA, RA, Anterior horns and 

 roots. CP, RP, Posterior horns and 

 roots. RA, Part of anterior horn whose 

 head CA has been detached. X, De- 

 cussation of lateral columns at pyra- 

 mids (P, P'). NP, Nucleus of poste- 

 rior pyramids, a and p, Anterior and 

 posterior median grooves. 



Section of Medulla Oblongata 

 at the Upper Part Sensory or 

 Fillet Decussation. (M. DUVAL.) 



OA, Head of anterior horn. C'A, 

 Base of anterior horn, nucleus of 

 hypoglossal nerve. H, Root fiber of 

 hypoglossal. 1, 2, 3, Anterior, lateral, 

 and posterior columns, x, x, Fibers 

 coming from the posterior columns 

 and forming sensory or fillet decussa- 

 ti-on in x. P, P', Pyramids. NR, Nu- 

 cleus of restiform body. NP, Goll's 

 nucleus. CP, Posterior horn. 



WHITE COLUMNS.- The direct 'pyramidal tract, whose fibers 

 decussate the length of the cord by traversing the white commissure, 

 do not cross at the level of the medulla. They pass directly into 

 this organ, to be placed in the anterior pyramid of the correspond- 

 ing side. At the level of the medulla the two principal anterior 

 columns, those of the right and left, which heretofore pursued a 

 parallel course, now separate from the median line. They carry 



