810 



THE NERVOUS SYSTEM 



1. The largest of them is the dentate nucleus. This is an isolated mass of 

 grey substance situated in the core of white substance of each hemisphere. It is 

 in the form of a folded or corrugated cup-shaped lamina, with the opening of the 

 cup (hilus) directed anteriorly and obliquely toward the mid-line. It contains a 

 mass of white substance and possesses a capsule. Its cell-bodies give rise to most 

 of the fibres forming the superior cerebellar peduncles. 



2. The nucleus emboliformis is an oblong and much smaller mass of grey 

 substance, which lies immediately medial to the hilus of the dentate nucleus. It 

 is probabh' of the same significance as the dentate nucleus, being merely a portion 

 separated from it. 



3. The nucleus globosus, the smallest of the cerebellar nuclei, is an irregular 

 horizontal mass of grey substance with its larger end placed in front. It lies 

 close to the medial side of the nucleus emboliformis, antl often appears separated 

 into two or more rounded or globular masses. 



4. The roof nucleus [nucleus fastigii] is the second largest of the cerebellar 

 nuclei, and is the most mesially placed. The pair is situated in the roof of the 



Fig. 637. — Section of Cerebellum and Brain-stem Passing Obliquely Through Inferior 

 Portion of Cerebellum to Superior Margin of Pons. (After Toldt, "Atlas of Human 

 Anatomy," Rebman, London and New York.) 



Posterior cerebellar notch 



Medullary lamina 

 Cortical substance 



Corpus meduUare 



Vermis (superior) 



Capsule of den- 

 tate nucleus 



Dentate nucleus 



Core of the dentate nucleus 



Hilus of dentate nucleus 



Brachium conjunctivum 



Fourth ventricle 



Fossa rhomboidea (pars superior) 



Stratum nucleare 

 Decussation of brachium 

 conjunctivum 



Pons (Varolii 



Nucleus 

 globosus 



Roof nucleus 



Nucleus emboliformis 



Lingula cerebelli 

 Anterior medullary velum 

 Substantia ferruginea 

 Lateral lemniscus 



Medial longitudinal fasciculus 

 Raphe of medulla oblongata 



"X^ Cerebral peduncle 

 Interpeduncular fossa 



fourth ventricle, and so near the mid-line that both nuclei are in the white sub- 

 stance of the vermis. They are ovoid in shape, and the nucleus of one side receives 

 axones from the nucleus of the vestibular nerve chiefly of the opposite side, the 

 decussation of these axones taking place in the vermis. Its cells are larger than 

 those of the two first-mentioned nuclei. 



The peduncles of the cerebellum. — The peduncles consist of three pairs — the 

 inferior, mifldlc, and superior. The three peduncles of each side come together at 

 the level of the lower border of the pons, and the entering and emerging fibres of 

 which they are composed become continuous with the central core of white sub- 

 stance of the cerebellar hemispheres. (Fig. 631, 638, 639.) 



The restiform body of the medulla oblongata is the inferior peduncle. It 

 forms the lateral boundary of the inferior portion of the fourth ventricle, and upon 

 reaching the level of the pons turns sharply backward into the cerebellum. In 

 the region of the turn it is encircled externally by fibres of the cochlear nerve. It 

 contains fibres, Vjoth ascending and descending, between the cerebellar cortex and 

 the structures below the cerebellum. 



Its fibres include: d) fibres from the spinal cord including the dorsal spino-cerebellar 

 fasciculus (direct cerebellar tract) and fjrobably a small jjroportion of the ascending fibres of 

 the superficial ventro-lateral spino-cerebellar fasciculus (Cowers' tract); (2) fibres from the 



