THE FORE-BRAIN OR PROSENCEPHALON 



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covered by the epithelial lining of this cavity; the medial part is covered by the 

 tela chorioidea of the third ventricle, and is destitute of an epithelial covering. 

 In front, the superior is separated from the medial surface by a salient margin, 

 the taenia thalami, along which the epithelial lining of the third ventricle is reflected 



ion to the under surface of the tela chorioidea. Behind, it is limited medially by 

 a groove, the sulcus habenulae, which intervenes between it and a small triangular 

 area, termed the trigonum habenulse. 



The inferior surface rests upon and is continuous with the upward prolongation 

 of the tegmentum (subthalamic tegmental region) , in front of which it is related to 

 the substantia innominata of Meynert. 



Thalamus 



Lateral ventricle 

 Caudate nucleus 

 Internal capsule 



Lentiform nucleus 



Corpus callosum 

 Choroid plexus of 

 lateral ventricle 

 Fornix 



Choroid plexus of 

 third ventricle 



Third ventricle 



Red nucleus 



Substantia nigra 

 Post. perf. substance 



mi 



Bane of peduncle 

 Nucleus of Luys 

 Tcenia hippocampi 



Gyrus dentatus 



Inferior cornu of lateral ventricle 

 Hippocampus 

 Caudate nucleus 



FIG. 717. Coronal section of brain immediately in front of pons. 





The medial surface constitutes the upper part of the lateral wall of the third 

 ventricle, and is connected to the corresponding surface of the opposite thalamus 

 by a flattened gray band, the massa intermedia (middle or gray commissure}. This 

 mass averages about 1 cm. in its antero-posterior diameter: it sometimes consists 

 of two parts and occasionally is absent. It contains nerve cells and nerve fibers; 

 a few of the latter may cross the middle line, but most of them pass toward the 

 middle line and then curve lateralward on the same side. 



The lateral surface is in contact with a thick band of white substance which 

 forms the occipital part of the internal capsule and separates the thalamus from 

 the lentiform nucleus of the corpus striatum. 



