234 



NERVOUS SYSTEM OF VERTEBRATES. 



of growth of the flocculus and paraflocculus, together with the 

 submersion of a part of the lateral lobes of lower vertebrates to 

 form the nucleus dentatus. 



Those portions of the cerebellum which become large and impor- 

 tant in mammals are subdivided by variously placed fissures which 

 are merely the result of mechanical conditions of growth and most 

 of which are of no importance except as they may serve as land- 



Fig. 119. A diagram representing the more fundamental and constant fissures 

 of the mammalian cerebellum spread out in one plane. After G Elliot Smith. 



marks in practical work. Those fissures which develop earlier in all 

 mammals may be regarded as the more primitive and important 

 and may be taken as the boundary lines of the chief divisions of 

 the cerebellum. Upon this basis the cerebellum may be divided 

 into (A) the floccular lobe, including the flocculus and para- 

 flocculus; and (B) the rest of the cerebellum; which is subdivided 



