THE BEAIN 



353 



The cerebellum is a large transversely elongated 

 mass, lying behind the hemispheres. It is divided 

 into a large median lobe, the vermis, and two 

 lateral lobes, to the outer sides of which are the 

 small roimded floccular lobes. 



The whole surface of the cerebellum is marked 

 by close-set folds, mainly transverse in direction. 



The medulla oblongata is the part of the brain 

 beneath and behind the cerebellum. It is some- 



FiQ. 61. — ^LepuB cuniculus. A longitudinal and vertical section of the 

 brain, taken in the median plane, (a. m. m.) 



A, pituitary body. AC, anterior commissure. AP, anterior pillar of the 

 fornix, seen in the wall of the third ventricle. C, cerebellum. C A, corpus 

 albicans. CC, corpus callosum. CH, inner surface of left cerebral hemisphere. 

 £*, body of the fornix. FM, foramen of Monro. G-, yelum interpositum. 

 1, infundibulum. MG, middle commissure. IN*, anterior lobe of corpora 

 quadrigemina, or 'nates.' O, olfactory lobe. OC, optic chiasma. OW, left 

 optic nerve. P, pineal body. PG, posterior commissure. PV, pons Varolii. 

 T, posterior lobe of corpora quadrigemina, or 'testis.' VA, velum medullee 

 anterius, or valve of Vieusaens. "VP, velum meduUae postertus. 



Ill, third ventricle. IV, fourth ventricle. V, fifth ventricle. 



what flattened dorso-ventrally, is widest in front, 



and gradually narrows behind, passing into the 



spinal cord. 



i. The velum meduILse anterius, or valve of 



Vieussens, is a thin transparent membrane, 



A A 



