114 



HUMAN PHYSIOLOGY. 



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 

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



FIG. 12. 



n, and of Fourth Ventricle, with the neighboring parts. 

 (From Sappey.) 



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

 pyramid. 



1. 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 

 united fibres then pass upward through the pons Varolii and crura cerebri, 

 and for the most part terminate in the corpus striatum and cerebrum. 



2. The lateral tract is continuous with the lateral columns of the cord ; 



