80 INTRODUCTION. 



an index of the extent of freedom possessed by the arm, has been 

 explained : it remains to shew with what structural modifications of the 

 carpus, metacarpus, and phalanges, its presence is consonant, and with 

 what it is incompatible. 



Among all the lower Mammalia, none approach, in structure of the 

 hand and arm, so near to Man as the Quadrumana : the differences, 

 however, are many and important. In the first place, the hand is 

 longer, in proportion to its breadth, than in Man, and this, more parti- 

 cularly in some groups than in others, in which, as in the Orangs, the 

 Gibbons, and Semnopitheci, the fingers are not only greatly elongated, but 

 79 the palm, instead of being expanded and 



concave on its inner aspect, is narrow 

 and flat, and tapers from the wrist. This 

 modification of form, together with the 

 comparative shortness and feebleness of 

 the thumb, is exhibited in the annexed sketch (fig. 79) of the hand of the 

 Orang, 



Confining our observations to the osseous structure of the hand, it is 



at once obvious, that the carpus, 

 in the Simise, occupies a very cir- 

 cumscribed space, compared with 

 the analogous part of the human 

 hand : the first step toward the 

 contraction of the carpus is here 



Hand of the Ora ng ,- a , carpU8; 6 , xnetacarpus; c, phalanges. ^^ . neverthe l esS) with cemin 



exceptions, as in the hand of the Orang (fig. 80), the number of bones in 

 the carpus exceeds, by one, that in the human carpus the second row 

 having five, instead of four, distinct bones ; the first row, four, as in Man. 

 The elongation of the metacarpal bones of the fingers is also remarkable, 

 while the metacarpal bone, and the two phalanges of the thumb altogether, 

 only extend to the termination of the metacarpal bone of the first finger. 

 In some of the Simise this degradation of the thumb is carried much 

 farther, the part being, if not absolutely wanting, reduced to a mere rudi- 

 ment. Compared with the hands of Man, those of the Simiae are rude and 

 imperfect instruments : constructed as tree-climbing organs, they are 

 incapable of the manipulations which the human hand executes with the 

 utmost facility ; notwithstanding, they adequately serve the wants of 

 these animals, and harmonize with their general economy. It is, 

 therefore, in accordance with their arboreal habits, that the hinder 

 graspers of the Simiae are as hand-like as the anterior, perhaps more 

 so : for, in these latter organs, the thumb is far more developed ; 

 never, indeed, becoming rudimentary, even in those instances in which 

 it is the most reduced in the anterior graspers. 



