THE ENCEPHALON 251 



THE ENCEPHALON. 



The encephalon is situated within the cranial cavity and is 

 commonly called the brain. Its gross divisions are the medulla 

 oblongata, the pom Varolii, the cerebellum, and the cerebrum. 

 All the other divisions are in a measure subordinate to the cere- 

 brum, though each division has individual functions. The 

 human brain weighs about 49^ ounces in the male and about 

 44 in the female. 



The Medulla Oblongata. 



Anatomy. The medulla oblongata, or bulb, joins the upper 

 extremity of the spinal cord and extends to the pons above. It 

 has a pyramidal shape, lies in the basilar groove of the occipital 

 bone, and is slightly flattened antero-posteriorly. It is about an 

 inch and a quarter in length, half an inch thick, and three-quar- 

 ters of an inch broad above. The anterior and posterior median 

 fissures of the cord are continued upward in the medulla; the 

 central canal terminates in the inferior angle of the fourth ven- 

 tricle. The anterior columns appear to be continuous with 

 the anterior pyramids of the medulla. These pyramids are situ- 

 ated just lateral to the anterior median fissure. The innermost 

 fibers of the pyramids are the continuations upward of the crossed 

 pyramidal tracts, and are seen to decussate in the median line; 

 the outermost fibers are the prolongations of the uncrossed pyr- 

 amidal tracts. The olivary bodies, oval in shape, are just exter- 

 nal to the anterior pyramids separated from them by a groove. 

 The restiform bodies make up the postero-lateral portion of the 

 medulla, and are external to the olivary bodies. They contain 

 fibers from the columns of Burdach, and contribute largely to 

 the formation of the inferior peduncles of the cerebellum. The 

 restiform bodies, diverging as they ascend, form the lateral 

 boundaries of the inferior division of the fourth ventricle. 

 Beneath the olivary bodies, and between the anterior pyramids 



