DISTINCTIVE CHARACTERISTICS OF MAN. 



43 



uals among ourselves, who have either been congeuitally deficient in the 

 anterior extremities, or who have subsequently lost them, practice only has 

 been required to enable the posterior to be turned to the like account. 



FIG. 2. 



Foot of Man, compared ^vith posterior extremity of Orang, 



25. When the comparison, of which the leading points have now been 

 sketched, is extended further, we meet with differences that cannot but be 

 accounted of far greater importance, both in degree and in kind, than those 

 already enumerated. Thus in the entire group of Platyrrhine Monkeys, we 

 find that the thumb is not opposable, but ranges with the other digits, so 

 that it can only be used consentaneously with them in the act of prehen- 

 sion ; while in the Ateles, or Spider-Monkey, the thumb is altogether want- 

 ing, and although a great-toe is present, it can neither be used like that of 

 Man for support, nor be opposed to the other digits as in the higher Quad- 

 rumana, the posterior and anterior extremities being strikingly assimilated 

 in structure, and being alike adapted to serve only as claspers. Among the 

 Baboons and Lemurs, moreover, we find that the conformation alike of the 

 anterior and of the posterior extremities is such as to assimilate them at 

 least as much to the lower quadrupedal as to the higher quadrumanous type; 

 so that between the two extremes of the series of which the anthropoid Apes 

 are the highest and the Baboons and Lemurs are the lowest members, there 

 is a far wider interval, as regards the conformation of the extremities, than 

 that which separates the former from Man, 



26. The next series of distinctive characters to be considered, are those 

 by which Man is adapted to the erect attitude. On examining his Cranium, 

 we remark that the occipital coudyles are so placed, that a perpendicular 

 dropped from the centre of gravity of the head would nearly fall between 

 them, so as to be within the base on which it rests upon the spinal column. 

 The foramen magnum is not placed in the centre of the base of the skull, 

 but just behind it; so that the greater specific gravity of the posterior part 

 of the head, which is entirely filled with solid matter, is compensated by 

 the greater length of the anterior part, which contains many cavities. There 

 is, indeed, a little over-compensation, which gives a slight preponderance to 

 the front of the head, so that it drops forwards and downwards when all the 

 muscles are relaxed ; but the muscles attached to the back of the head are 

 far larger and more numerous than those in front of the coudyles, so that 



