MEDULLA OBLONGATA. 



83 



the medulla spinalis in the cavity of the cranium. It is likewise termed 

 mesocephale, from its being continuous with the spinal marrow in one 

 direction, and sending towards the brain strong prolongations crura 

 ' cerebri ; and to the cerebellum similar prolongations crura cerebelli ; 

 so that it appears to be the bond of union between these various parts. 

 In its lower portion, it seems to be merely a continuation of the me- 

 dulla spinalis, except that it is more expanded superiorly where it joins 

 the pons Varolii. This portion of the medulla oblongata is called, by 

 some, tail of the medulla oblongata; by others, the rachidian bulb; 

 and, by others again, it is regarded as the medulla oblongata. Its 

 lower surface rests on the basilary gutter of the occipital bone, and 

 exhibits a groove which divides the spinal cord into two portions. On 

 each side of this furrow are two oblong eminences, 

 the innermost of which is called corpus pyramidale, 

 the outermost, corpus olivare, which arise from the 

 anterior column of the medulla spinalis, or are a 

 continuation and subdivision of this column. These 

 oval bodies are surrounded by a superficial groove, 

 which, in some instances, is partially interrupted by 

 some arciform fibres, which cross it at its lower part. 

 At the lower third of the medulla oblongata, fibres 

 of the anterior pyramids decussate, and form an 

 anatomical demarcation between the medulla oblon- 

 gata and the spinal cord. The decussation takes 

 place by from three to five bundles of fibres from 

 each pyramidal body. This decussation, as will be 

 seen, hereafter, is interesting in regard to the cross 

 effect induced by certain diseases of the brain. On 

 the posterior surface of the medulla oblongata, the 

 posterior fasciculi separate to form the fourth ven- 

 tricle: at the sides of this ventricle are the corpora Anterior View of the 

 restiformia, or inferior peduncles of the cerebellum, Medulla Oblongata, 

 so called because they seem to aid in the forma- 

 tion of that part of the encephalon ; and on the in- 

 ner side of each corpus restiforme is the small 

 body the posterior pyramid. Again, in addition 

 to the corpora pyramidalia and olivaria which de- 

 rive their origin from, or are continuous with, the ^sating fibres. oi. 



. & . . . ' , tero-lateral column of 



anterior fasciculi ot the spinal cord, and are destined, the spinal cord. c . An- 

 according to some, to form the brain and the cor- 

 pora restiformia, which are continuations of the . 

 posterior fasciculi, and are destined to form the cere- 

 bellum, there exists, according to some anatomists, other fasciculi in 

 the rachidian bulb. All these are interesting points of anatomy, but 

 are not of so much importance physiologically; notwithstanding even 

 the views promulgated by Sir Charles Bell. 1 He considers that a 

 column exists between the corpora olivaria and corpora restiformia, 



1 The Nervous System of the Human Body : from Transactions of the Royal Society from 

 1821 to 1829, London, 1830. Reprinted in this country, Washington, 1833. 



showing the decus- 

 sation of the Pyra- 

 mids, and of the up- 

 per par I of the Spinal 

 (Jord. (After Mayo.) 



p. Anterior pyramids. 

 r. Restiform bodies, o. 

 Olivary bodies, d. De- 



anterior commis - 



