MEDULLA OBLONGATA. 127 



MEDULLA OBLONGATA. 



The Medulla Oblongata is the expanded portion of the upper part of 

 the spinal cord. It is pyramidal in form and measures one and a half 

 inches in length, three-quarters of an inch in breadth, half an inch in 

 thickness, and is divided into two lateral halves by the anterior and pos- 

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



FIG. 13. 



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. Inferior peduncle of the cerebellum, formed by the 

 restiform body. 4. Posterior pyramid : above this is the calamus scriptorius. 5. Supe- 

 rior peduncle of cerebellum, or processus e cerebello ad testes. 6 6. Fillet to the side 

 of the crura cerebri. 77. Lateral grooves of the crura cerebri. 8. Corpora quad- 

 rigemina, After Hirschfeld and Leveille. 



half is again subdivided by minor grooves, into four columns, viz. : anterior 

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

 pyramid. 



I. The anterior pyramid is composed partly of fibres continuous with 

 those of the anterior column of the spinal cord; but mainly of fibres de- 

 rived from the lateral tract of the opposite side, by decussation. The 



