IN THE LIMBS OF MAMMALIA. 75 



of the fingers, unless the proper extensors of the first, second, and fifth digits are remaining 

 portions of it ; the only common extensor, like the superficial flexor, having been moved 

 as to its origin, two segments above its normal position, like the short extensor. 



In creneral, the muscles, like the bones of the posterior extremities, repeat in an opposite 

 direction those of the anterior, but the exact correspondences between individual muscles 

 are far more difficult to determine than would be expected, either from the apparently 

 more simple functions of the limbs as such, or from the close antitypy exhibited by their 

 osseous framework. Moreover, extended and minute comparisons of parts have as yet 

 been almost wholly confined to anthropotomy, a branch of comparative anatomy which 

 treats of a structure teleologically most perfect, but morphologically monstrous. 



The legs are usually regarded as very simple and regular in their structure, because 

 their only function is that of locomotion ; but it is from this very cause that they are more 

 complicated than the corresponding limbs of quadrupeds, for they are also the only organs 

 of locomotion, and therefore are required to maintain the equilibrium of the erect body 

 during progression, a duty which in the four-footed members of the class, is shared by the 

 anterior extremities. 



By a sort of favoritism shown to the anterior, and physiologically more noble region of 

 the body, when the functions of prehension are transferred from the quadrupedal head to 

 its diverging appendages, the arms, these are in their turn allowed to impose upon their 

 posterior representatives their share in sustaining and propelling the body ; but the latter, 

 less highly favored, can merely make an awkward protest when the kangaroo throws upon 

 the base of his huge caudal appendage the task of supporting his body while he kicks out 

 with his hind legs, and when certain monkeys suspend themselves by the other end of their 

 tails so as to leave all their limbs free. 



The natural position of the quadruped is sustained in part according to physical laws, as 

 is a table upon its four pedestals ; but that of man is in direct defiance of these laws, which 

 are ever ready to assert their rights the moment his will ceases to guard against them ; 

 and he, the lord of creation, is obliged to take his rest in an attitude other than that in 

 which his superiority is exercised ; his elevation is great, but according to the law of the 

 succession of extremes, his fall is proportionately great, when the means of that elevation 

 are withdrawn ; he pays as it were, a physiological price for his plrysiological preeminence. 



As in the arms of man were found extra muscles and articulations, with direct reference 

 to the superadded function of rotation, so in the lower limbs there appears to be an 

 increase in the number of muscles, and changes in the relation of those which are morpho- 

 logically entitled to be present, in view of the fact that by two legs, instead of four, is the 

 body to be propelled and its equilibrium maintained ; therefore, they cannot be regarded 

 as presenting the normal condition of parts for correcting our ideas as derived from the 

 arms, since they are quite as fully, though less obviously and directly, under teleological 

 influence. 



The real extent of the antitypical relations between the anterior and posterior extremi- 

 ties must be learned from those vertebrates in whom they are actually fore and hind; and 

 for this, when time and opportunity allow, such works as that of Strauss-Durckheim on 

 " the Anatomy of the Cat ; " of Della-Chiaje on that of the Testudo Europanx ; and of Meckel 

 on that of the Ornithoryncus, with the more comprehensive work of the latter anatomist, 

 " Traite generale d'Anatomie comparee," will be invaluable. Prior to these investigations, 

 any such inferences as may now be drawn from the human structure must be regarded as 

 provisional and by no means as conclusive. 



