200 



HUMAN EMBRYOLOGY AND MORPHOLOGY. 



4th month (Fig. 164) and by the 6th month are larger than the 

 median lobe. 



vermis 



nodule 



,'at. lobe 

 cerebellum 



lot. lobe 



ligula 

 for. Majendie 



■lot. recess 

 inf. med. uelum 



obex. 



claua 

 ucleus. cuneatus 

 ueleus. gracilis 



Fig. 164. — Diagram of the Attachments of the Inferior Medullary Velum in a 5th 

 month foetus. (After Kollmann.) 



Only in the higher primates are the lateral lobes well 

 developed. In the 2nd and 3rd months the simple transverse 

 roof plate is transformed by the outgrowth from its surface of 

 five transverse ridges. As these ridges or foliae grow out (Fig. 

 166) the anterior two of them come to occupy the upper surface, 

 while the three posterior ones are thrust to the lower surface. 

 The folding of the simple cerebellar plate, so that it comes 

 to present an upper and lower surface, is caused by its growth. 

 The secondary and tertiary foliae are produced in the last three 

 months of foetal life. 



corp. bigem. 



cerebellum 



-inf. med. uelum. 



3rd vent 



;;ftCe~entral canal 



aqueduct 4th ue "t"'cle 



Fig. 165. — Median Section of the Cerebellum and 4th Ventricle of a Frog. 



The three Peduncles of the cerebellum are produced thus — 

 probably during the latter half of intra-uterine life : 



(1) The Superior. — Fibres grow from the cells of the dentate 



