362 DK. G. ELLIOT SMITH ON 



that the combinod jiodunciilar masses are not visible in a profile view. In the exuberance 

 of its growth the mesial cej)halic and mesial caudal parts of the cerebellar mass bend in 

 the ventral direction, and become tucked in between the two pillar-like masses formed 

 by the cerebellar peduncles. These cephalic and caudal cerebellar processes come into 

 apposition between the columnce cerehelli (as we may call the combined peduncles) and 

 thus produce a deep vertical transverse slit, which Ave may call the superior recess of the 

 fourth ventricle {recessus superior) (vide fig. 29). 



Fii;. 29. 



Mesial sagittal section of the cerpbclliim of Or^iclerojpus. Enlarged -^ rliam. 



Anteriorly the cerebellum is in close contact Avith the posterior extremities of the 

 cerebral hemispheres, and this contact adapts the configuration of the anterior margin of 

 the cerebellum, so that a prominent rostrum is formed projecthlg forward from its 

 antero-superior margin in the mesial plane. This rostrum projects into the interhemi- 

 spheral cleft, and partly roofs over the posterior corpora quadrigemina. 



Although the surface of the cerebellum is evenly rounded in Orycteropus and does 

 not present any of those sudden projections Avhich are found in many mammals, it 

 cannot he considered even or smooth. On the contrary, the sui-face of the organ will be 

 found on all sides to present slight gradual elevations and gentle depressions, and these 

 hills and vales give the organ an irregularly-corrugated appearance. The surface of the 

 cerebellum is everywhere marked Avith an exceedingly complicated pattern of lines, 

 labyrinthine in its intricacy. These lines, the arrangement of which Ave shall find to 

 conform to a more or less definite and orderly plan, represent the situation of the deep 

 fissures, Avhich cut up the whole mass of the cerebellum into a complex mass of narrow 

 leaf-like folds. These folds are mutually adaptive, and are so closely packed that the 

 whole complex oi folia forms a solid organ. 



The lateral poles of the cerebellum are formed of two large bodies, each composed 

 of a complex mass of folia. These masses are almost completely separated from the ' 

 rest of the cerebellum by fissures Avliich cut deeply into the organ until they reach 

 the medullary matter. As the area thus separated oft' on each pole from the rest of 

 the cerebellum includes the homologue of the flocculus of human anatomy, and is a 

 natural division of the organ, we may distinguish it as the lobus flocculi, and the deep 

 limiting fissure as i\\e fisswra floceii t i . The latter corresponds to the pm-afloccular sulcus 



