130 THE STRUCTURE OF MAN 
If we take the average weight of the body of a Chimpanzee 
from two to four years old as 84 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) 
Be 
Fria. 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 httle 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 
