356 THE INTERMEDIATE PRIMATES 



The dimensions of the brain inchiding the eerebelhim and brain stem arc: 



Longitudinal 78 mm. 



Transverse or interparietal 67 mm. 



Total weight of the brain 1 26 gms. 



Weight of the forebrain 109 gms. 



Weight of the midbrain 2 gms. 



Weight of the hindbrain 15 gms. 



Total volume of the brain, determined by water dis- 

 placement 1 20 c.c. 



Vokimc of the forebram 100 c.c. 



Volume of the midl:)ram 2 c.c. 



Volume of the hindbrain 18 c.c. 



Upon the basis of these figures, compiited on the weight of the several 

 portions of the brain, the following encephalic indices were determined for 

 the several divisions of the brain: 



Forebrain index 84 per cent 



Midbrain index 2 per cent 



Hindbrain index ■ 14 per cent 



Macacus rhesus, possessmg as it docs a forebrain mdex of 84 per cent, 

 comes by this reason naturally into the group of those animals in which 

 manual development has progressed to a marked degree. This index places 

 the animal distinctly higher than any of the lower primates. 



Surface Appearance of the Brain in Macacus Rhesus 

 lobes and fissures 



The convexity of the hemisphere shows much the same characteristic 

 arrangement as in baboon. The region of cortex comprised between the 



