794 MAN 



tentorial surface of the cerebellum which has lost much of its transverse 

 convexity. It manifests none of that sharp gabling so prominent in the 

 lower and intermediate primates. Even the ridge-pole effect produced 

 by the vermal portion of the cerebellum is almost completely lost, and while 

 this cerebellar surface is not actually flat, it much more nearly approaches 

 this condition than in any of the forms already described. The most 

 cephalic portion of the superior vermis is still somewhat protrusive, extending 

 slightly above the general plane of the tentorial surface. The interfolial sulci 

 pass almost without demarcation from vermis to lateral lobes and the folial 

 delineation is, if anything, slightly more pronounced than in the lower species. 

 This cerebellar expansion, which appears to have confined itself so largely to 

 the lateral lobes, accords with the expansion discernible in the cerebral hemi- 

 spheres. It offers a convincing argument as to the pronounced increment in 

 the several functional areas of the encephalon. The indications of expansion 

 evident upon the tentorial surface of the cerebellum become more 

 pronounced on the occipital surface. The posterior cerebellar notch has 

 become deep and the vallecula so much depressed below the surface that it 

 requires a separation of the lateral masses of the cerebellum to reveal the now 

 almost concealed inferior vermis. The two apposite borders of the lateral 

 cerebellar lobes arc in contact with the falx cercbclli. The appearance of this 

 surface gives such outstanding prominence lo the lateral lobes as to make the 

 vermal portion of the organ seem almost insignificant. \\ hen the lateral lobes 

 are separated, two deep paramedian sulci are brought to view, which appar- 

 ently interrupt the continuity of the vermal sulci as they pass into the 

 lateral lobes. Upon the petroso-vcntricular surface of the cerebellum, all of 

 the usual landmarks are prominent, including the cerebello-pontile angle, the 

 great horizontal fissure and the middle peduncle. In every feature, this 

 portion of the brain, which has its prototype in the brainsof all lower primates, 

 reaches its greatest definition in man. 



