356 



THE BRAIN 



Behind and somewhat below the diencephalon lie^ the 

 mesencephalon or mid-brain. It is separable into ( i ) a dorsal 

 portion, the lamina quadrigemina or tectum, which is divided 



Massa intermedia 



Fornix 



Gyrus cinguli 



Caudate nucleus in lateral ventricle '\ \ 

 Remnant of septum pcllucidum 

 Genu of corpus callosvim ' 

 Superior frontal gyrus \ 



Callosal sulc 

 Sulcus cingu 



Inferior surface of fornix 

 I Superior surface of thalamus 

 i Upper end of central sulcus 

 I r Splenium of corpus callosum 

 ,' { r Paracentral lobule 



lian part of transverse fissure 

 Pineal body 



Lamina quadrigemina 

 UectumJ 



rietal sulcus 

 Calcarine fissure 



Gyrus rectus 

 Rostrum of corpus callosu 



Anterior commissure 

 Lamina terminals 

 Supra-optic recess' 



Optic chiasma / 

 Arrow passing through inter- 

 ventricular foramen ' 



Infundibulum / 



Mamillary body 

 Oculo-motor nerve 



Peciunculus cerebri 



ngual gyrus 

 Cerebellum 



^ Fourth ventricle 



Median aperture of fourth ventricle 



entral canal of spinal medulla 



Medulla spinalis 



FIG. 136. Medial surface of the Right Hemisphere, and the structures seen 

 after a sagittal section has been made through the Corpus Callosum, the 

 Fornix, the Diencephalon, the Mesencephalon, and the Rhomben- 

 cephalon, and after the Septum Pellucidum has been removed from 

 between the Corpus Callosum and the Fornix. The arrow passes 

 through the interventricular foramen from the right lateral ventricle to 

 the third ventricle, where it lies in the hypothalamic sulcus in the side 

 wall of the third ventricle. 



by a longitudinal and a transverse sulcus into four rounded 

 bodies called the colliculi or corpora quadrigemina (Fig. 195) ; 

 and (2) a ventral part, cut by a depression, the interpeduncular 

 fossa, into two rounded columns, the pedunculi cerebri. The 

 mid-brain is traversed, between the lamina quadrigemina and 



