Chap. XIX.] 



DURING UTERINE LIFE. 



341 



indicative of the almost complete absence at this j)eriocl of 

 the Median Lobe. 



On examining the base of the brain, the Medulla is 

 found to be large. The ' anterior pyramids/ and the rudi- 

 ments of the ' olivary bodies ' outside them, are quite 

 distinctly recognizable. A thin band, marked by a median 

 furrow, is to be seen stretching across between the lateral 

 lobes of the Cerebellum. This is the first trace of the 

 ' pons Varolii.' In front of it are the Cerebral Peduncles ; 

 between these latter are the ' corpus albicans' and the 

 ' tuber cinereum,' and in 

 front of this last lies 

 the * commissure ' of the 

 Optic Nerves. All the 

 other cerebral nerves are 

 distinctly recognizable, 

 though they are ex- 

 tremely slender at this 

 period. 



After this epoch the Fig. 128. -The outer surface of the Foetal 

 T - , f, .-, 1 • Brain at Six Months. (Sharpey, after R. Wagner.) 



aeveiOpment 01 the bram This and the next figures are intended to show 

 S'OeS on according" to *^® commencement of the formation of the 

 . ' , ^ principal fissures. F, Frontal lobe ; P, parietal ; 



Gratiolet, with most SUr- O, occipital ; T, temporal ; a a a, slight appear- 

 ^•„' ■ 1-j -D 4-1, « f'nce of the several frontal convolutions ; ss, the 



prismg rapidity. By the ^^,^^^ ^3,,,,, . ,,^ ,,^ ^^.^^.^^ ^j^j^.^^'^ ^; ,j^^ 



end. of the 5tll month, ^^ttorn of it, C, the central lobe or island of Reil ; 

 ., 1 f. 1 /-i '■' fissure of Rolando ; p, the external perpen- 



the groAvth of the Cere- dicuiar fissure. 

 bral Hemispheres has 



been so great that they completely cover not only the 

 Corpora Quadrigemina but also the now larger Cerebellum. 

 The ' fissure of Sylvius ' is wide and open (fig. 128), so as 

 to leave uncovered the central lobe or ' island of Eeil.' 

 The beginning of the ' fissure of Rolando ' is, at this period, 

 sometimes recognizable, while the rudiments of convolutions 

 are to be traced upon the frontal lobes and other parts. The 



