io66 



HUMAN ANATOMY. 



The Lateral Area. — This region is defined on the surface by the antero-lateral 

 and postero-lateral furrows in Iront and behind respectively, and includes a narrow 

 strip on the lateral aspect of the medulla. Below, the tract is continuous with the 

 lateral column of the cord, a resemblance which is, however, only superficial since 

 within the medulla the large crossed pyramidal tract no longer lies laterally but 

 within the anterior area of the opposite side. The upper part of the lateral area is 

 conspicuously modified by the presence of an elongated oval prominence, the olivary 

 eminence (oliva), produced by the underlying corrugated lamina of gray matter 

 composing the inferior olivary nucleus. The olive measures about 13 mm. in length 

 and about half as much in its greatest width. Its upper end, more prominent and 

 slightly broader than the lower, is separated from the inferior border of the pons by 

 a deep groove, which medially joins the furrow occupied by the hypoglossal root- 

 fibres and laterally is continuous with a broad depressed area, \\\^ paraolivary fossa, 

 that separates the olive from the restiform body and lodges the fibres of the glosso- 

 pharyngeal and pneumogastric nerves. The demarcation of the lower tapering end 

 of the olive is somewhat masked by the anterior superficial arcuate fibres, which cover 

 for a variable distance the inferior part of the olive in their course backward to gain 



Thalamus 



Pulvinar 



Fig. 917. 



Lateral geniculate body 



Median geniculate body 

 Inferior brachium 



Superior colliculus 

 Cerebral peduncle 

 Inferior colliculus 



Superior cerebellar peduncle 



Superior medullary velum 

 Middle cerebellar peduncle 



Line of attachment of 

 roof of IV ventricle 

 Inferior cerebellar peduncle 

 (restiform body) 



Clava 



Tuberculum cuneatuni 



Tuberculum Rolandi 



Superior brachium 



Mesial root of optic tract 



Anterior perforated space 



Optic tract 

 — Lateral olfactory root 



Optic nerve 

 Optic commissure 

 Tuber cinereum 



Mammillary body 



Olivary eminence 

 -Arcuate fibres 



-Lateral area of medulla 



Brain-stem viewed from the side, showing lateral aspect of medulla, pons, and mid-brain. 



the restiform body. The components of the lateral column of the cord traceable into 

 the medulla — the direct cerebellar and Gowers' tract and the long paths of the lateral 

 ground-bundle — for the most part, with the exception of the direct cerebellar tract, 

 pass beneath or to the outer side of the olive. The superficially placed direct cere- 

 bellar tract gradually leaves the lateral area and passes outward and backward to join 

 the inferior cerebellar peduncle by which it reaches the cerebellum. 



The Posterior Area. — The posterior region of the medulla is bounded laterally 

 by the fibres of the ninth and tenth nerves ; and mesially, in the lower half of the 

 bulb, by the posterior median fissure and, in the upper half, by the diverging sides 

 of the fourth ventricle. Below, the posterior area receives the prolongations of the 

 tracts of Goll and of Burdach, which within the medulla are known as the funic- 

 ulus gracilis and funiculus cuneatus respectively, and are separated from each 

 other by the paramedian sulcus. Beginning with a width of about 2 mm. , the gra- 

 cile funiculus increases in breadth as it ascends until, just before reaching the lower 

 end of the fourth ventricle, it expands into a well-marked swelling, the clava, about 

 4 mm. wide, which is caused by a subjacent accumulation of gray matter. Then, 

 diverging from its fellow of the opposite side to bound the ventricle, after a short 

 course it loses its identity as a distinct strand and becomes continuous with the 



