NERVOUS SYSTEM. VERTEBRATA. 435 



D. 649. The brain of a nearly adult female Orang-Outang (Simla 

 satyrus) . 



This excellent specimen admirably demonstrates the lii^h 

 vaulting and rotundity of the hemispheres and the 

 extent of the prominent orbital keel and consequent ex- 

 cavation of the orbital surface. 



The floccular lobe of the cerebellum is distinctly larger 

 than that of the last specimen ; the difference in size 

 appears to chiefly affect the paraflocculus, which is much 

 the larger of the two lobules, and is also exposed, as in the 

 lower Apes. 



On the right cerebral hemisphere there is a peculiar 

 arrangement of the superior limiting sulcus of Reil, which 

 seems to end in a T-piece so as to simulate the Y-shaped 

 disposition of the anterior rami of the human Sylvian 

 fissure. A short branch of the fronto-orbital sulcus affords 

 a further indication of the closing-in of the anterior insular 

 area. 



By its irregular mode of union with the oblique sulcus 

 the arcuate contributes to the formation of a very irregular 

 and asymmetrical pattern. The inferior frontal (" rectus ") 

 sulcus is simple and well-developed on each hemisphere. 



The upper frontal region is occupied by such an irregular 

 group of scattered, disjointed sulci that it is impossible to 

 say which are superior or middle frontal elements. 



There is a typical (Primate) intraparietal sulcus. The 

 ranms postcentralis superior is separate on both sides : it 

 is particularly well developed on the right side, but broken 

 up into four irregular fragments on the left. 



The Sylvian fissure has a bifid extremity on both sides. 

 But the hooked extremity of the parallel sulcus is not 

 nearly so complete as in the last specimen. 



The broad plump arcus occipitalis is wholly exposed on 

 both sides. 



The occipital operculum is now quite small. 



0. C. looo H. 



D.650. The brain of an Orang-Outang (Simla satyrus). The 

 left hemisphere has been detached. 



This specimen is especially interesting because all 

 sulci are gaping as a result of the treatment of the brain 



