THE BRAIN. 



407 



Fig. 1 19. Transverse sections through the fore-brain of a four and one-half weeks 

 embryo. (Gordinier and Quain after His.) 



A. Through the lower anterior part of the fore-brain. S. Falx. Sf. Fold of roof passing 

 below falx toward the third ventricle. Bf. Fold forming the fissura hippocampi. v.Rl.,k.Rl. 

 Anterior and posterior parts of olfactory lobe. Cs. Corpus striatum. O.W. Groove con- 

 tinuous with optic stalk. P.s. Hypothalamus. T.c. Tuber cinereum. 



B. Section a little farther back. Sf is replaced by a less prominent but broader fold of 

 the roof, Ad, which subsequently receives the chorioid vessels, and is, therefore, the chorioid 

 fold. Hs. Hemisphere vesicle. Th. Thalamus. S.M. Sulcus hypothalamicus (Monroi), 

 below and behind the thalamus. 



C. Still farther back. Ad. Chorioid fold here projecting into lateral ventricles, but still 

 free from mesoblast and blood-vessels. Ma. Mammillary tubercle. The other lettering as 

 before. 



