

NERVOUS SYSTEM. VERTEBRATA. 421 



D.627. The brain of a Chacma Baboon (Papio porcarius), (<?). 

 The left hemisphere has been detached. [The right 

 hemisphere has been damaged by a horizontal saw- 

 cut.] 



There is an exceptionally well-developed anterior limiting 

 sulcus of Reil or, as it is more generally known, fronto- 

 orbital sulcus. External to this there is a short deep sulcus 

 [best seen on the right hemisphere] just in front of the 

 exposed end of the superior limiting sulcus of Reil, that 

 emerges from the Sylvian fissure. This is of great interest 

 because it indicates that extension of the surface in this 

 region which in a slightly higher phase of development 

 leads to the formation of an operculum. An examination 

 of the series of brains of Anthropoid Apes shows that this 

 operculum is often formed by the upper lip of a small 

 sulcus in this position, which is not part of either the 

 superior (Marchand's " opercular ") or the anterior 

 (fronto-orbital) limiting sulcus. 



The collateral sulcus is unusually extensive, its caudal 

 end almost joining the calcarine sulcus, and its anterior 

 end overlapping the rhinal fissure. There is, therefore, no 

 separate occipito-temporal sulcus such as we find in the 

 brain of some Baboons. 



On the left hemisphere there are small superior pre- 

 central and superior frontal sulci of diagrammatic sim- 

 plicity. 0. C. 1338 A. 



[For fuller information concerning this brain, see 

 D. J. Cunningham, Mem. Roy. Irish Acad. vol. iii. 1892, 

 p. 282.] 



D. 628. The brain of a Chacma Baboon (Papio porcarius). The 

 left cerebral hemisphere has been separated. 



The peculiarly extensive collateral sulcus of the pre- 

 ceding specimen is exactly reproduced here also. 



On the left hemisphere, the opercular lip of the Simian 

 sulcus has been pulled backward sufficiently far to show 

 that the relations of the intraparietal sulcus and that which 

 we may now call " parieto-occipital " are essentially the 

 same as those described in specimen D. 630 (vide tnfra). 



0. C. 1338 A i. 



