82 



MEDULLA OBLONGATA. 



having the same disposition as the crura cerebri. They are the crura 

 cerebelli. 



Owing to the peculiar arrangement of the white and gray cerebral 

 substances, when one of the hemispheres of the cerebellum is divided 

 vertically, an arborescent appearance is presented, the trunks of the 

 arborization being white, the surrounding substance gray. This ap- 

 pearance is called arbor vitas. The part where all these arborizations 

 meet, near the centre of the cerebellum, is called corpus denticulatum 

 vel rhombo'idale. Gall was of opinion, that this body has great agency 

 in the production of the cerebellum. Lastly, the cerebellum covers the 

 posterior part of the medulla oblongata, and forms with it a cavity, 

 called fourth ventricle. 



The medulla oblongata is so called, because it is the continuation of 



Analytical Diagram of the Encephalon in a Vertical Section. (After Mayo.) 



5. Spinal cord. r. Restiform bodies passing to c, the cerebellum, d. Corpus dentatum of the cere- 

 bellum, o. Olivary body. /. Columns continuous with the olivary bodies and central part of the 

 medulla oblongata, and ascending to the tubercula quadrigemina and optic thalami. p. Anterior pyra- 

 mids, v. Pons Varolii. n, b. Tubercula quadrigemina. g. Geniculate body of the optic thalamus. 

 t. Processus cerebelli ad testes. a. Anterior lobe of the brain, q. Posterior lobe of the brain. 



