ANKLE-JOINT. 53 



spends to the radius. Nature, by one of those transforma- 

 tions of which she furnishes numerous examples, has united 

 the two extremities of the ulna and radius in one, allowing 

 the first of these bones to exist only as a rudiment in its upper 

 portion. This blending of two organs is termed by naturalists 

 a coalescence. The resemblance of the tibia to the radius 

 was remarked by De Blainville, and has been demonstrated 

 by M. Martins in his beautiful work on the pelvic and 

 thoracic limbs. 



The lower extremities of the tibia and fibula united form 

 a mortise, in which the astragalus, one of the bones of the 

 tarsus, is received, and thus constitute the tibio-tarsal articula- 

 tion, or articulation of the foot. The foot moves upon the leg 

 in such a manner as to form with it a straight line when 

 extended. The movement in an opposite direction, or flexion, 

 is much more limited, the two mallcoli which embrace the 

 astragalus not permitting lateral movements in the foot, those 

 which do take place being made by the articulation of the 

 astragalus with the other parts of the tarsus, though a limited 

 movement of circumduction can be made by the foot. 



It has been said that the foot is another hand -pes alter a 

 manus and if the hand completes the arm, so does the foot 

 complete the leg. Without it locomotion could not be 

 effected except by movements quite different from those of 

 walking, and under conditions of equilibrium much less 

 favourable, and with much greater fatigue; running, and 

 consequently jumping, would be impossible. But if the foot 

 and the hand are varieties of the same type of organization, 

 they present differences in regard to their respective uses; 

 the foot, designed to support the body, is especially remark- 

 able for its solidity; in the hand mobility is the predomi- 

 nating quality. 



The foot of man, exclusively designed for the support of 

 the body, is not an organ of prehension, and cannot, like the 

 foot of the monkey, take hold of objects by opposing the 

 thumb to the other fingers ; the toes, disposed upon the same 

 plane, have neither the length of the fingers nor the extent 

 and variety of their movements; in a word, it is a foot and 

 not a hand, as it is in the quadrumana. 



