THE MEDULLA OBLONGATA AND BRAIN STEM 489 



sensory portions of this latter group of cranial nerves arise, or 

 rather their peripheral neurones terminate, in the medulla oblon- 

 gata in the cell groups of the dorsal horns which lie in the floor 

 of the fourth ventricle and not far removed from the median 

 line ; this is the case with the tenth, ninth, and a part of the ves- 

 tibular portion of the eighth nerves. In the upper rhomben- 

 cephalon, at the level of the pons Varolii, the dorsal grey nuclei, 

 though more laterally situated, are displaced somewhat ventral- 



FIG. 382. TKANSECTION OF THE LOWER MEDULLA OBLONGATA OF MAN, AT THE LEVEL 

 OF THE MOTOR DECUSSATION. 



(7a', anterior horn ; Cac, central canal ; Dpy, motor decussation ; FcV, accompanying 

 tracts of the trigeminus; /we, column of Burdach ; fng, column of Goll ; fsla, anterior 

 median fissure ; JET, Helwig's fasciculus ; J5T/S, direct cerebellar tract ; Ncu, nucleus of Bur- 

 dach ; Ng, nucleus of Goll ; NXId, dorsal nucleus of the spinal accessory nerve ; P, Pick's 

 bundle ; Py, pyramid ; Sgl, substantia gelatinosa of Eolando ; /SW, lateral reticular sub- 

 stance ; Trs, the rubro-spinal tract, Monakow's bundle ; Tscv, antero-lateral ascending 

 (Gower's) tract ; Fa, bundle of Vicq d'Azyr ; VG, anterior ground bundle ; XI, spinal 

 accessory nerve. Weigert's stain, x 5. (After Marburg.) 



ward. In this region is the lateral group of sensory nuclei of the 

 cranial nerves, which includes a portion of the vestibular group, 

 the acoustic nuclei, and the sensory nucleus of the trigeminus. 



Besides the grey nuclei which are thus continued up from the 

 spinal cord, several additional centers occur in the rhomben- 

 cephalon as isolated masses of grey matter which are without 

 homologues in the lower segments of the cerebro-spinal axis. 



The first of these are the nuclei of Goll and Burdach, in which 

 the postero-internal and postero-external columns of the spinal cord 



