G28 



NERVOUS SYSTEM. 



20.' 



two anterior pyramids, one on either side. Viewed superficially, the inner- 

 most fibres of these pyramids are seen to decussate in the median line ; but 

 if the fibres be traced from the cord, it is found that they come from the 

 crossed pyramidal tracts of the lateral columns and that none of them are 

 derived from the anterior columns. The fibres of the external portion of 

 the anterior pyramids come from the direct pyramidal tracts of the cord. 

 At the site of the decussation, the pyramids are composed entirely of white 



matter ; but as the fibres spread out to pass to 

 the encephalon above, they present nodules of 

 gray matter between the fasciculi. 



External to the anterior pyramids, are the 

 corpora olivaria. These are oval and are sur- 

 rounded by a distinct groove. They are white 

 externally and contain a gray nucleus called 

 the corpus deutatum. 



External to the corpora olivaria, are the 

 6 restiform bodies, formed chiefly of white mat- 

 ter and constituting the postero-lateral portion 

 of the medulla. They are continuous with 

 the posterior white columns of the cord. The 

 restiform bodies spread out as they ascend, 

 and pass to the cerebellum, forming a great 

 portion of the inferior peduncles. Some fibres 

 from the restiform bodies pass to the cere- 

 brum. 



Beneath the olivary bodies and between 

 the anterior pyramids and the restiform bod- 

 ies, are the lateral tracts of the medulla, some- 

 times called the intermediar or lateral fascic- 



These are 

 , , . . . 



composed of an intimate mixture of white and 



matter and havp a vpllmvinh orav pnlnr 

 & ld J m l IldVC d jeilOWlSIl-gldy C 



They receive all that portion of the antero- 

 lateral columns of the cord which does not 

 enter into the composition of the anterior 

 1 ! J, % PJ ramids - The - v are usuall y described as parts 

 dura mater of the cord ; is, optic o f the restiform bodies, but they are peculiarly 



tracts ; 16, chiasm of the optic 



nerves; 17, motor ocuii communis ; important, from the fact that they contain 



18, patheticus ; 19, fifth nerve : 20, i J 



motor ocuii extemus ; 2i. facial the gray centre presiding over respiration ; 



nerve : 22. auditory nerve : 23. nerve c J L 



of wrisberg ; 24, giosso-pharyngeai and f or that reason they are here described as 



nerve ; 25, pneumogastric ; 26, 26, . 



spinal accessory ; 27, sublingual distinct faSClCllll. 



nerve ; 28, 29, 30, cervical nerves. . -i / /. T \ 



The posterior pyramids (fumculi graciles) 



are the smallest of all. They pass upward to the cerebellum, without decus- 

 sating, joining the restiform bodies above. They are composed chiefly of 

 white matter. As they pass upward in the medulla, they diverge, leaving a 

 space at the fourth ventricle. 



FIG. 231. Anterior view of tlie medulla llli, or the funicilli of Rolando. 

 oblongata (Sappey). 



1, infundibulum ; 2, tuber cinereum ; 

 3, corpora albicantia : 4. cerebral 

 peduncle ; 5, pons Varolii ; 6, origin 

 of the middle peduncle of the cere- 

 bellum ; 7, anterior pyramids of 

 the medulla oblongatn ; 8, decnssa- 

 tion of the anterior pyramids ; 9, 





