THE BRAIN 



343 



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

 telencephalon, and laterally in this region the optic vesicles develop. Into 

 each optic stalk extends the optic recess (Fig. 343). 



Diencephalon 



l.Iesencephalon 



Pallium 



Corpus mammillare 



Tuber cinereum 



Pars ant. olf. lobe 

 Pars post. olf. lobe 



Infundibulum Ototic stalk 

 FIG. 346. Lateral view of the fore-brain and mid-brain of a 13.6 mm. embryo (His). 



Lateral ventricle 



Cliorioid plexus of lateral 

 ventricle 



Thalamus 

 Corpus striatum 



Third ventricle \ 



FIG. 347. Transverse section through the fore-brain of a 15 mm. embryo, showing the early 

 development of the chorioid plexus and fissure (His). 



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

 cerebral hemisphere (Fig. 331). It is already prominent in embryos of 

 six weeks (13.6 mm.), bulging into the lateral ventricle (Figs. 345 and 347). 

 It is in line caudally with the thalamus of the diencephalon and in develop- 



