THE MEDULLA OBLONGATA AND BRAIN STEM 491 



is distinguished from the more lateral grey reticular formation 

 (formatio reticularis grised) ; in contradistinction this is known 

 as the white reticular formation (formatio reticularis alba). 



At the mid-level of the medulla oblongata a small portion of 

 the lateral column moves obliquely dorsal ward to enter the cere- 



ffiul 



FIG. 383. TRANSECTION OF THE HUMAN MEDULLA OBLONGATA AT THE LEVEL 

 OF THE LOWER MARGIN OF THE INFERIOR OLIVARY BODY. 



Cac, central canal ; cH, central tract of the tegmentum ; do, dorso-olivary fibres ; 

 faed, the dorsal external arcuate fibres ; faev, the ventral external arcuate fibres ; /a?', the 

 internal arcuate fibres ; Fe V, accompanying tracts of the trigeminus ; IXa, spinal root of., 

 the glosso-pharyngeus ; IXa', accessory bundle of the same ; KS, direct cerebellar tract ; 

 Lm, mesial lemniscus ; Na, nucleus ambiguus ; NarcP, arcuate nucleus of the pyramids ; 

 Nee, external nucleus of Burdach ; Ncu, nucleus of Burdach ; Ng, nucleus of Goll ; Nit, 

 nucleus of the lateral column ; Nmd, dorso-marginal nucleus of Ziehen ; No, inferior 

 olive ; NX, dorsal vago-glosso-pharyngeal nucleus ; NXId, dorsal spinal accessory nu- 

 cleus ; NXII, hypoglossal nucleus ; Oae, accessory olivary nuclei ; Py, pyramids ; Sgl, 

 gelatinous substance of Rolando ; Trs, rubro-spinal tract (Monakow's bundle); Tscv, an- 

 tero-lateral ascending tract of Gowers ; Tst, spino-tectal and thalamic tract ; VNo, olivary 

 capsule ; vo, ventro-olivary fibres ; XII, hypoglossal nerve. Weigert's stain, x 5. 

 (After Marburg.) 



bellum. These fibres are reinforced by a considerable bundle com- 

 ing from the cerebellum to enter the inferior olivary body. To- 

 gether these bundles form a projecting column of white matter 

 in close relation to the substantia gelatinosa of Rolando in the tips 

 of the dorsal grey horns ; this mixed tract is the restiform body 



