THE BRAIN 



341 



The third ventricle extends some distance into the caudal end of the telen- 

 cephalon and laterally in this region develop the optic vesicles. Into each optic 

 stalk extends the optic recess (Fig. 325). 



Dicnccphalon 



Mcsencephalo 



Corpus mammillarc 



Tuber cinerea 



Pallium 



Pars aiil. off. lobe 



Pars post. olf. lobe 

 Jufuiidibulum Oplic stalk 



Fig. 32S. — Lateral view of the fore-brain and mid-brain of a 13.6 mm. embryo (His). 



Lateral ventricle 



Chorioid plexus of lateral 

 ventricle 



Thalamus 

 Corpus striatum 



T/iird ventricle 



Fig. 329. — Transverse section through the fore-brain of a 16 mm. embryo showing the early develop- 

 ment of the chorioid plexus and fissure (His). 



The corpus striatum is developed as a thickening in the floor of each cerebral 

 hemisphere. It is already prominent in embryos of five weeks (13.6 mm.) bulg- 

 ing into the lateral ventricle (Figs. 327 and 329). It is in line caudally with the 



