54 



THE BRAIN 



its lateral walls are formed by the medial surfaces of the 

 two thalami. A little anterior to the middle of the ventricle 

 the cavity is crossed by the massa intermedia, which connects 

 the thalami with each other, and anterior to this the column 

 of the fornix is seen descending in the lateral wall. At first 

 the column is distinct and prominent, but as it approaches 

 the corresponding corpus mamillare it gradually becomes 



Sulcus hypothalamicus Corpus callosum 



Massa intermedia 

 ( ' Thalamus 

 ,' ; Taenia thalami 

 ( ' ,' ' Mesencephalon 



,' ,' ' Pineal body 



Chorioid plexus 

 Column ' 

 of fornix '. 



For. interventriculare 

 Septum pellucidum 



Germ 



Anterior 

 commissure 

 Corpus mamillare 



/ Quadrigeminal bodies 

 / Splenium 



Aquaeductus cerebri 



Lamina terminalis ' 



Optic nerve 



Hypophysis '' ' 



Tuber cinereum 

 Oculo-motor nerve / 

 Pons 



Anterior medullary velum / 

 Ventricle iv. ' 

 Medulla oblpngata ' 

 Chorioid plexus 

 in Ventricle iv. 



Culmen monticuli 



Declive monticuli 



Folium 

 vermis 



Tuber vermis 



Pyramid 



Uvula 



Central lobule 

 Nodule 



FIG. 207. Median section through the Corpus Callosum, Third Ventricle, 

 Mesencephalon, Pons, Cerebellum, and Medulla Oblongata. 



more ? and more sunk in the grey matter on the side of the 

 ventricle. 



The roof 'of the third ventricle is formed by a thin epithelial 

 layer which stretches across the median plane, from the one 

 tsenia thalami to the other, and is continuous with the 

 remainder of the epithelial lining of the cavity. It is applied 

 to the under surface of the tela chorioidea, which overlies the 

 ventricle, and is invaginated into the cavity by the chorioid 

 plexuses which hang down from the under surface of that 

 fold of pia mater. In the removal of the tela chorioidea 

 the thin epithelial roof was torn away. 



The third ventricle communicates freely with the lateral 



