CEREBRAL HEMISPHERES 



117 



The rhinencephalon at this stage is quite uncovered by the pallium and separated 

 from it by the external rhinal fissure (fig. 155). It extends back to the extremity of 



!/iir. o/facl. med. 



cerebellum 



it. of Rr 



gyr. olfact. lat. 



gyr. ambient 



gur. semiJunaris 



oliue 



FIG. 160. BRAIN OF A FCETUS AT THE BEGINNING OF THE FOURTH MONTH, 

 FROM BELOW. (From Kollmann.) 



The gyrus olfactorius lateralis, gyrus ambiens, and gyrus semilunaris together form tlie 



lobus pyriformis. 



parietal lobt 



olfactory bulb 



gyr. olf. laferalis 



</ii/\ scmilunaris 

 riyr. ambiens 



FIG. 161. BBAIN OF A FOETUS AT THE BEGINNING OF THE FOURTH MONTH. (From Kollmann.) 



the temporal horn ; but as the temporal pole grows downwards and forwards, its 

 posterior extremity becomes covered over, and ultimately reversed in position, 



