THE MAMMALS 



455 



feet. Brain capacity is often used as an index of intelligence, and from 

 this standpoint the gibbons are far below the other apes and man. They 

 have a capacity of only 90 cc. on the average. A modern civilized man, 

 on the other hand, has a capacity of about 1500 cc, but there is a primi- 

 tive race, the Australian aborigines, which have a brain capacity of only 

 1200 cc. Of course, some allowance must be made for the smaller size 



Courtesy Chicago Park District 



Fig. 28.31. A gorilla. Although among the most powerful of animals, gorillas are 

 hard to keep in captivity because they are susceptible to many human diseases. This 

 is Bushman at the age of seventeen in the Lincoln Park Zoo in Chicago; he died a 



few years later. 



of the gibbon. In one respect, however, they are more man-like than 

 the other apes. They walk erect without touching their arms to the 

 ground, but holding them out to their sides as balancers. 



The orangutans of Borneo and Sumatra are probably more human- 

 like in facial features than any of the group. There is no development 

 of the heavy brow ridges, which may give other apes a somewhat fero- 

 cious appearance, rftiir on the face grows in the same region that it 

 does on man's face and a portrait of an orangutan, at first glance, might 



