THE BRAIN OR ENCEPHALON 



859 



In its simplest expression the brain is a tube like the rest of the central nerve 

 axis, but a remarkably modified one. lucre is the same primitive ependymal 



B 



PONS 

 CEPHALIC FLEXURE 



CORPUS ALBICANS 

 TUBER CINEREUM 



OLFACTORY FOLD/ 



FIG. 627. Profile view of the brain of human embryos at three several stages, reconstructed from sections 

 A. Brain of an embryo of about fifteen days. B. Brain of an embryo about three and a half weeks old. C. 

 Brain of an embryo about seven and a half weeks old. (After His.) 



lining throughout its interior; there is likewise a central tubular gray mass of 

 ganglionic tissue which, however, undergoes nuclear differentiation in some 



