STRUCTURE OF THE APE AND MAN. 211 



sponding complexity or perfection of structure ; the trunk 

 is adjusted to accord with the actions of such instruments, 

 and the brain is developed in proportion with the power 

 of executing so great a variety of actions and movements 

 as the four-handed structure gives capacity for. 



In the skull of the quadrumana are seen indications of 

 a concomitant perfection of the outer senses ; the orbits 

 are entire, and directed forwards, with their outlets almost 

 on the same plane; both eyes can thus be brought to bear 

 upon the same object. The rest of the face, formed by 

 the jaws, now begins to bear a smaller proportion to the 

 progressively expanding cranium. The neck, of mode- 

 rate length, has its seven vertebrae well developed, with 

 the costal processes large in the fifth and sixth : the dorsal 

 vertebra3, twelve, in the species figured {Pithecus satyrus\ 

 show, by the convergence of their spines towards the ver- 

 tical one on the ninth, that this is the centre of movement 

 of the trunk. The lumbar vertebrae are four in number; 

 in the inferior monkeys they are seven, and the anterior 

 ones are firmly interlocked by well-developed anapophy- 

 ses and metapophyses. The sacrum is still long and 

 narrow. The tail, in some of the lower quadrumana, is 

 of great length, including 30 vertebrae in the red monkey 

 {Cereopithecus ruber), in which the anterior ones are com- 

 plicated by having haemal arches. The clavicles are en- 

 tire in all quadrumana. The humerus has its tuberosities 

 and condyloid crests well developed. The radius rotates 

 freely on the ulna. The wrist has nine bones, owing to 

 a division of the scaphoid, besides supplementary sesa- 

 moids adding to the force of some of the muscles of the 

 hand; the thumb is proportionally shorter in the fore than 

 in the hind foot. The patella is ossified, and in most 

 baboons and monkeys there is a fabella behind each con- 



