xi BRAIN 501 



(/. t), and extends into the infundibulum below. At its 

 anterior end are the foramina of Monro (/. m), leading 

 into the middle of the lateral ventricles in the hemispheres 

 (Fig. 141). In this region each lateral ventricle is broad 

 from side to side, but narrow from above downwards ; 



FIG. 142. Rabbit. Longitudinal vertical section of the rabbit's brain. (X ij.) 

 L< 'tiers as in preceding figure ; in addition cb. central lobe of cerebellum, showing 

 arbor vitae ; c. c. crus cerebri ; c. h^. parietal, and cp. h~. temporal lobe of 

 cerebral hemisphere ; c. ma. elevation behind the infundibulum ; /. m. foramen 

 of Monro ; inf. infundibulum ; /. t. lamina terminals ; ly. part of hippocampus ; 

 m. o. medulla oblongata ; o. ch. optic chiasma ; pty. pituitary body ; vl. ip. 

 choroid plexus ; v. vn. valve of Vieussens ; //. optic nerve. (From Parker's 

 Zootoiny.} 



it extends forwards into the frontal lobe, backwards into 

 the parietal lobe, and downwards into the temporal 

 lobe. The olfactory lobes are solid. 



A prominent, convex ridge of white matter the hippo- 

 campus (Fig. 141, hp. m) projects into the inner side and 

 floor of each lateral ventricle where it descends into the 

 temporal lobe, and closely applied to it is a continuation of 

 the choroid plexus (ch. pi), which passes from the roof of the 

 third ventricle into the lateral ventricle through the foramen 

 of Monro. In front of the hippocampus the outer side and 

 floor of the anterior part of the lateral ventricle is thickened 

 to form an eminence of grey matter, the corpus slriatum 

 (cp. s). Just beneath the corpus callosum the internal wall 

 of each lateral ventricle is thin, and is known as the septum 

 lucidum (sp. lu) ; and below it and above the foramina of 

 Monro is another commissure known as the body of the 

 fornix (Figs. 141 and 142, b.fo] which is continuous on either 



