112 



NERVOUS SYSTEM 



cilia are gradually closed, and the vesicles remain attached by the optic stalks. 

 The history of the vesicles will be considered in the chapter on the development of 



ri.iencephalon 



-* 



amillary region ^ 



optic stalk 



infundibulum 

 FIG. 153. MODEL OF THE BRAIN OF A HUMAN EMBRYO OF 10'2 MM. (FIFTH WEEK). (His.) 





infundibulum 



optic recess 



FIG. 154. THE SAME MODEL AS IN FIG. 153 FROM THE MESIAL ASPECT. 



The large opening into the hemisphere-vesicle is the foramen of Monro. On the wall of the 

 cliencephalon the sulcus of Monro is seen separating the thalamus (dark-shaded area) from the 

 hypothalamus (lighter-shaded area). 



of diencephalon 



mamillary region 



infundinulum 



FIG. 155. MODEL OF THE BRAIN OF A HUMAN EMBRYO OF 13 - 6 MM. 

 (BEGINNING OF SIXTH WEEK) FROM THE SIDE. (His.) 



