410 



PHYSIOLOGICAL SERIES. 



is useful to enter into a somewhat minute examination of a 

 Macaque's brain, not only that we may emphasize those 

 common mammalian features which become obscured in the 

 Simiidae and especially in Man, but also because the brain 

 of Macacus has been so often explored by physiological 

 methods that the homologies of its various parts thus acquire 

 an added interest. 



The olfactory bulb (which has been destroyed in this 

 specimen) is a small ellipsoidal mass of grey matter. A- ;i 

 result of the great forward extension of the cerebral 

 hemispheres in the Anthropoidea, the place of attachment 

 of the olfactory peduncle to the hemisphere becomes removed 



Fig. 242. (x.) 



SULC.CEN7 



SULC. ARC. 

 SULC. RECT. 



RAM ; US.POSTC.SUP- 



SULC.INTRAPAR. 



SULC. SIM. 



SULC.L.OCC. 



SULC. INF. OCC. 



SULC. INF. TRANS. 



SULC. PAR. 



progressively further away from the cribriform plate of the 

 ethmoid bone, where the olfactory bulb is, as it were, 

 moored by the olfactory nerves. The olfactory peduncle 

 therefore becomes greatly elongated, and a.< \\ roult the 

 proportion of grey matter to white fibres (olfactory tract) 

 becomes greatly reduced, so that the peduncle becomes a 

 long, attenuated, white ribbon. In most Cercopithecid 

 brains no olfactory sulcus is developed to accommodate this 

 flattened peduncle. 



The relations of the olfactory p< dnnele to the tuberculnm 

 olfactorium and pyriform loin- are identical with those so 

 clearly demonstrable, say, in the brain of a Dog or of a Sheep. 

 The tuberculum olfactorium is still very distinct, because it 

 has not become flattened out to the same extent as it li;i> in 

 the human brain. A very pronounced flexure has occurred 



