138 MAN AND APES. 



In the first place, the height of the Orang's 

 cerebrum in front is greater in proportion 

 than in either the Chimpanzee or the Gorilla ; 

 while the brain of the last-named animal falls 

 below that of the Chimpanzee, in that it is 

 relatively longer and more depressed, as com- 

 pared with man's brain. 



Each half of the cerebrum is divisible into 

 four parts or lobes (Fig. 54 — 57.) The 

 first of these (marked 1, 2, and 3) is the 

 " frontal." The second (marked 4, 5, and 6) 

 is the " parietal." The third (marked 10, 11, 

 and 12) is the "occipital,-" and the fourth 

 (marked 7, 8, and 9, in Fig. 54, 7, 6, 9) is the 

 " temporal." 



On comparing the brain of man with the 

 brains of the Orang, Chimpanzee, and Baboon, 

 we find a successive decrease in the frontal 

 lobe, and a successive and very great increase 

 in the relative size of the occipital lobe. 

 Concomitantly with this increase and de- 

 crease, certain folds of brain substance, called 

 " bridging . convulsions " (marked -a and /3), 



