CH. XLVI.] 



INTERIOR OF CEREBRUM. 



643 



band of transverse commissural fibres known as the corpus callosum. 

 The interior of each hemisphere contains a cavity of complicated 

 shape called the lateral ventricle ; the lateral ventricles open into 

 the third ventricle. The corpus callosum is shown in fig. 476. 



Fi?- 477. Dissection of brain, from above, exposing the lateral, fourth, and fifth ventricle* 

 with the surrounding parts. J. a, anterior part, or genu of corpus callosum ; b, corpus 

 utriatum ; b', the corpus striatum of left side, dissected so as to expose its grey sub- 

 stance ; c, points by a line to the teenia semicircularis ; d, optic thalamus ; , anterior 

 pillars of f ornix divided ; below they are seen descending in front of the third ventricle, 

 and between them is seen part of the anterior commissure ; in front of the letter e is 

 seen the slit-like fifth ventricle, between the two laminae of the septum lucidum ; /, 

 oft or middle commissure ; <j is placed in the posterior part of the third ventricle ; 

 immediately behind the hitter are the posterior commissure (just visible) and the 

 pineal gland, the two crura of which extend forwards along the inner and upper 

 margins of the optic thai ami ; h and i. the corpora quadrigemina ; k, superior cms of 

 cerebellum ; close to k is the valve of Vieussens, which has been divided so as to 

 expose the fourth ventricle ; I, hippocampus major and corpus fimbriatum, or ta?nia 

 hippocampi ; m, hippocampus minor ; n, eminentia collateral!* ; o, fourth ventricle ; 

 p, posterior surface of medulla oblongata ; r, section of cerebellum ; i, upper part of 

 left hemisphere of cerebellum exposed by the removal of part of the posterior cerebrul 

 lobe. (Hinchfeld and Leveilie.) 



The next figure (fig. 477) represents a dissected brain in which 

 the corpus callosum has been removed ; the ventricles are thus 

 exposed. 



Each hemisphere is covered with grey matter, which passes 

 down into the fissuies that abound on its exterior. This surface 



T T 2 



