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). 



Mesencephalpn 



Diencephalon 



Pallium 



\ 



Corpus mammillare 



Tuber cincreum 



\ 



Pars ant. olf. lobe 



Pars post. olf. lobe 

 Infundibulum Optic stalk 

 FIG. 328. Lateral view of the fore-brain and mid-brain of a 13.6 mm. embryo (His). 



Lateral ventricle 



Chorioid plexus of lateral 

 ventricle 



Thalannis 

 Corpus striatum 



Third 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 



