448 



HUMAN ANATOMY.. 



The bones in front of the astragalus and os calcis move very much as a unit, 

 although there may be some play between the scaphoid and cuboid and between the 

 latter and the fifth metatarsal. The astragalus, having no muscle inserted into it, is 

 acted on in the ankle-joint by tke other bones, as is the first row of the carpus, its 

 motions depending on the pressure it receives. When the foot is in extreme dorsal 

 flexion all the joints of the tarsus are locked and no motion is possible. Starting 



Fig. 463. 



Tibia 



Astragalus 



Calcaneo- 



aslragaloid 



ligament 



Internal sesamoid bone 



Scaphc 



Expansion 

 from tibialis 

 posticus Sustentaculum 



Inferior calcaneo-scaphoid ligament 



Longitudinal section through right foot in axis of first metatarsal bone. 



from a position of moderate flexion, the motions (excepting those of simple flexion 

 and extension which occur in the ankle) are combinations of adduction and abduction, 

 inversion and eversion. Adduction is generally combined with inversion, and these 

 two motions are more extensive than the opposite ones. They practically never 

 occur pure. Inversion and eversion occur chiefly in the joints below the astragalus, 

 but in part in the mid-tarsal joint. Adduction and abduction are perhaps about 

 equally divided between the two ; but if the calcaneum be held by one hand and the 



Internal 

 cunei- 

 form 



Fig. 464. 



Middle cuneiform 



External cuneiform 



Internal 

 cuneiform 



Cuboid 



Interosseous ligament 



Transverse section through cuneiform bones of right foot, 

 seen from behind. 



Fig. 465. 



Middle cuneiform 



External cuneiform 



Cuboid 



Fifth 



meta- 



^VsL';'!*" tarsal 



interosseous ligaments 



Oblique section through cuneiform bones of right foot, 

 seen from behind. 



front of the foot moved by the other, it is clear that the mid-tarsal joint allows much 

 more abduction and adduction than eversion and inversion, which therefore occur 

 chiefly between the calcaneum and astragalus. 



In the ordinary position of supporting the body it appears that the essential arch 

 is through the calcaneum, the cuboid, the external cuneiform, joined to the latter by 

 a firm interosseous ligament, and the third metatarsal.* This can be proved by 



^ H. V. Meyer : Der menschliche Fuss. 



