THE MEDULLA OBLONGATA. 



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THE MEDULLA OBLONGATA. 



The medulla oblongata is the expanded portion of the upper part 

 of the spinal cord. It is pyramidal in form and measures i l /2 inches 

 in length, ^ of an inch in breadth, y 2 of an inch in thickness, and 

 is divided into two lateral halves by the anterior and posterior median 

 fissures, which are continuous with those of the cord. Each half 

 is again subdivided by minor grooves into four columns viz., an- 

 terior, pyramid, lateral and tract olivary body, restiform body, and 

 posterior pyramid. 

 .1. The anterior pyramid is composed partly of fibers continuous 



with those of the anterior column of the spinal cord, but mainly of 



FIG. 23. VIEW OF CEREBELLUM IN SECTION, AND OF FOURTH VENTRICLE, WITH 

 THE NEIGHBORING PARTS. {From Sappey.) 



i. Median groove fourth ventricle, ending below in the calamus scriptorius, 

 with the longitudinal eminences formed by the fasciculi teretes, one on 

 each side. 2. The same groove, at the place where the white streaks of 

 the auditory nerve emerge from it to cross the floor of the ventricle. 3. In- 

 ferior peduncle of the cerebellum, formed by the restiform body. 4. Pos- 

 terior pyramid; above this is the calamus scriptorius. 5, 5. Superior 

 peduncle of cerebellum, or processes e ccrebello ad testes. 6, 6. Fillet 

 to the side of the crura cerebri. 7, 7. Lateral grooves of the crura cerebri. 

 8. Corpora quadrigemina. {After Hirschfeld and Leveille.) 



fibers derived from the lateral tract of the opposite side by 

 decussation. The united fibers then pass upward through the pons 

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