THE NERVOUS SYSTEM 487 



Externally, the medulla shows the continuation upward of the 

 anterior fissure and posterior septum of the cord. On either side of 

 the anterior fissure is a prominence caused by the anterior pyramid, 

 and to the outer side of the pyramid the bulgin<^ of the olivary body 

 may be seen. The antero-lateral surface of the medulla is also 

 marked by the exit of the fifth to the twelfth (inclusive) cranial 

 nerves. The VI and XII (somatic motor) emerge near the mid- 

 ventral line, the others, including the splanchnomotor portions of the 

 V, VII, IX and X, emerge more laterally. The posterior surface 

 shows two prominences on either side. The more median of these, 

 known as the clava, is caused by the nucleus gracilis, or nucleus of 

 the column of Goll; the other, the cuneus, lying just to the outer side 

 of the clava, is due to the nucleus cuneatus or nucleus of the column 

 of Burdach. Lateral to this is a third eminence, the tuber culum 

 cmere/fw, due in part to the descending root of the V and its underlying 

 terminal nucleus, the continuation of the dorsal gray column of the 

 cord. This eminence merges anteriorly with the eminence of the 

 restiform body. The central canal of the cord continues into the me- 

 dulla, where it gradually approaches the dorsal surface and opens into 

 the cavity of the fourth ventricle. The floor of the fourth ventricle 

 exhibits a medial eminence occupied caudally by the nucleus hypo- 

 glossi (trigonum hypoglossi). Lateral to this is a triangular area, the 

 ala cinerea {trigonmn vagi), surrounded by furrows. This is partly 

 occupied by nuclei of the vagus. Cephalad and laterally a broader 



Fig. 331. — Principal afferent and efferent suprasegmental pathways (excepting the 

 rhinopallial connections, the efferent connections of the midbrain roof and the olivo- 

 cerebellar connections). Efferent peripheral neurones of cranial nerves are omitted. 

 Each neurone group (nucleus and fasciculus) is indicated by one or several individual 

 neurones. Decussations of tracts are indicated by an X. ac, Acoustic radiation, from 

 medial geniculate body to temporal lobe; br. conj, brachium conjunctivum (superior 

 cerebellar peduncle); br. pontis, brachium pontis, from pons to cerebellum; b.q.i, 

 brachium quadrigeminuminferius; e.g./, lateral or external geniculate body; c.g.m, medial 

 or internal geniculate body; c.quad, corpora quadrigemina;/.cor/.-5/>,pallio-spinal fascic- 

 ulus (pyramidal tract); f.c.-p.f, frontal pallio-pontile fasciculus (from frontal lobe); 

 f.c.-p.t, temporal pallio-pontile fasciculus (from temporal lobe); f.c.-p.o, occipital 

 pallio-pontile fasciculus (from occipital lobe);/.c«w, fasciculus cuneatus (column of 

 Burdach); t.f.-b, fastigio-bulbar tract;/, grac, fasciculus gracilis (column of Goll); f.s.-t, 

 spino-thalamic fasciculus; /.^/'.-c.f/, dorsal spino-cerebellar fasciculus (tract of Flechsig); 

 f.sp.-c.v, ventral spino-cerebellar fasciculus; lem. lat, lateral lemniscus or lateral fillet; 

 Icm. vied, medial lemniscus or fillet; n. coch, cochlear nerve; n.cmi, (terminal) nucleus of 

 the column of Burdach; 7i.d, nucleus of Deiters; 7i.dent, nucleus dentatus; n.grac, nucleus 

 of the column of Goll; n.opt, optic nerve; n.r, nucleus ruber; 7i.t, nucleus tecti (or fastigii) ; 

 n.trig, trigeminal nerve; n.vesl, vestibular nerve; pes.ped, pes pedunculi (crusta); ptilv 

 thai, pulvinar thalami; pyr, pyramid; rad. ant, ventral spinal root; rad. post, dorsal spinal 

 root; rad. opt, optic radiation (from lateral geniculate bod\^ to calcarine region) ; 50?k<e5. 

 bundles from thalamus to postcentral region of neopallium; sp. gang, spinal ganglion; 

 t.f.-b., tractus fastigio-bulbaris; thai, thalamus; t.7i.d, tract from the nucleus of Deiters; 

 t. riib.-sp, rubro-spinal tract (von ]\Ionakow). (Lateral view of brain.) 



