130 THE STRUCTURE OF MAN 



If we take the average weight of the body of a Chimpanzee 

 from two to four years old as 8 J kilogrs., and the average weight 

 of brain as 343 grs., we shall have 1 : 24'7 as the relative 

 weight of the latter. An Orang of the same age appears to 

 possess a rather heavier brain (1 : 22'3 or 340 : 7600). A 

 comparison of these two Anthropoids with Man, the ratio of 

 whose brain weight to his body weight between the second and 

 fourth years ranges from 1:18 to 1:16, shows that the 

 difference at this age is not great, as would seem natural when 

 we recall the greater similarity to human beings shown by 

 young Anthropoids. In older Chimpanzees (90-106,6 cm. long) 



IP. 



FIG. 82. CEREBRUM OF A HUMAN EMBRYO SEVEN TO EIGHT MONTHS OLD. 



(Lateral View.) 

 References as for Fig. 79. 



the relative brain weight is markedly lower, viz. 1 :42,5 (391 : 

 16650) or 1:52 (375,6:19500). It is probable, however, 

 that the average brain weight in older Chimpanzees is con- 

 siderably lower, as in a body weighing 28 kilogrs. it scaled 

 1 : 75. If this is the case, a comparison with an adult human 

 being, in whom the average brain weight is 1:40-35, shows 

 that the brain of Man is relatively at least twice as heavy as 

 that of the Chimpanzee, and absolutely three or four times 

 as heavy. We learn from this that the brain of the Ape, unlike 

 that of Man, develops little with age, and attains its definitive 

 condition far sooner. 



The Chimpanzee and the Orang appear to have approxi- 

 mately the same brain weights, but the Gorilla stands markedly 

 distinct from them, its body being far larger, while its brain 

 does not correspondingly increase in size. The weight of the 

 body of an adult Gorilla being taken at 94-95 kilogrs., and the 



