xxiv. 3 BRACHIATORS 629 



and are provided with very powerful muscles, the hands and feet being 

 efficient grasping organs. There is no tail. These brachiating habits 

 have affected the entire skeleton. All the apes and men differ from the 

 cercopithecids in having wider chests, longer necks, longer limbs, and 

 larger heads (Fig. 408). The cervical and sacral regions are longer in 



Fig. 409. Mandibles of A, *Parapithecus; B, *Propliopithecus; C, *Pliopithecns, 

 D, Hylobates. Dental arches of E, Gorilla; F, *Dryopithecus; G, *Plesianthropus; 



H, Homo. 



(A-D after Le Gros Clark, B.M. Guide, and Gregory; E-H after Howells, 



Mankind So Far, Doubleday and Company, Inc.) 



apes than in the monkeys and the lumbar region shorter. When pro- 

 ceeding on the ground the apes cannot balance on two legs for long; 

 instead, the long forearms prop up the front of the body and produce 

 a semi-erect position. The hands are specialized for brachiating, with 

 a short thumb and long metacarpals and digits (Figs. 410 and 411). 

 The foot is in general similar but in the chimpanzee and gorilla it is 

 more suited for walking, with broader sole and shorter toes. In the 

 terrestrial Gorilla gorilla beringei the hallux lies parallel to the other 

 toes almost as in man. 



The teeth (Fig. 409) are of a rather generalized type. The canines 

 are often large, especially in males, and the lower front premolar forms 



