338 



DEVELOPMENT OF THE HUMAN BRAIN 



upper and posterior margin of this ventricle the ' Pineal 

 body' soon appears, and also its 'peduncles ' which extend 

 forwards on each side. 



By the 12th week of intrauterine 

 life, the configuration of the Brain has 

 undergone a very marked change ; first 

 by reason of the increased size of the 

 Cerebellum, (fig. 123, C, c) which is now 

 thicker and marked by a median longi- 

 tudinal furrow, though otherwise smooth 

 on its surface; and, secondly, by the still 

 more striking development of the Cere- 

 bral Hemispheres (C, a), which have 

 already grown so much backwards as com- 

 pletely to overlap the 'third ventricle' 

 (fig. 123, jP, 8). On the under surface of 

 each Hemisphere an Olfactory Lobe is 

 now very distinct, as a hollow bud-like 

 outgrowth, the cavity of which is con- 

 tinuous with that of the Hemisphere 

 from which it projects. 



The ' lateral ventricles ' themselves 

 spnai cord'f^tuTol are, moreover, continuous with the cavity 

 Four Months, seen from O f fa e Thalamencephalon, or ' third ven- 



behind. (Sharpey, after . i n /? 



Hemi- tricle,' by an opening on each side ot 

 ** anterior extremity, known by the 

 c, Cerebellum ; name O f the 'foramen of Munro.' Near 

 this opening a transverse band begins to 

 ing overlapped by the appeai . (above and in front), which 



Cerebellum ; s s, the cer- ri . a i 



vicai and lumbar swell- connects the two hemispheres and is 



ings of the spinal cord. thouglit to correspon( l w i tn the COm- 



mencement of the great transverse commissure, the Corpus 

 Callosum, and perhaps also with the Anterior Commis- 

 sure. The walls of the Cerebral Hemispheres are very 



