94 



TARSUS ASTRAGALUS OS CALCIS. 



Fig. 37 * 



posticus ; by the posterior surface, to the popliteus and flexor longus 

 pollicis. 



TARSUS. The bones of the tarsus are seven in number ; viz. the 

 astragalus, os calcis, scaphoid, internal, middle, and external 

 cuneiform and cuboid. 



The ASTRAGALUS may be recognised by a rounded head, a broad 

 articular facet upon its convex surface, and two articular facets, 

 separated by a deep groove, upon its concave surface. 



The bone is divisible into a superior and inferior surface, an ex- 

 ternal and internal border, and an anterior and posterior extremity. 

 The superior surface is convex, and presents a large quadrilateral 

 and smooth facet, somewhat broader in front than behind, to articu- 

 late with the tibia. The inferior surface is concave, and divided 

 by a deep and rough groove, which lodges a strong interosseous 

 ligament, into two facets the posterior large and quadrangular, 

 and the anterior smaller and elliptic, which articulate with the os 

 calcis. The internal border is flat and irregular, and marked by a 

 pyriform articular surface, for the inner mal- 

 leolus. The external presents a large triangular 

 articular facet, for the external malleolus, and is 

 rough and concave in front. The anterior ex* 

 tremity presents a rounded head, surrounded by 

 a constriction somewhat resembling a neck ; and 

 the posterior extremity is narrow, and marked by 

 a deep groove, for the tendon of the flexor longus 

 pollicis. 



Hold the astragalus with the broad articular 

 surface upwards, and the rounded head for- 

 wards; the triangular lateral articular surface 

 will point to the side to which the bone belongs. 

 Articulations. With four bones; tibia, fibula, 

 calcis, and scaphoid. 



The Os CALCIS may be known by its large size 

 and oblong figure, by the large and irregular 

 portion which forms the heel, and by two articu- 

 lar surfaces, separated by a deep groove upon 

 its upper side. 



The os calcis is divisible into four surfaces, 

 superior, inferior, external, and internal ; and 

 two extremities, anterior and posterior. The superior surface is 

 convex behind and irregularly concave in front, where it presents 

 two and sometimes three articular facets, divided by a broad and 

 shallow groove, for the interosseous ligament. The inferior surface 



* The dorsal surface of the left foot. 1. The astragalus; its superior quadrilateral 

 and articular surface. . 2. The anterior extremity of the astragalus, which articulates 

 with (4) the scaphoid bone. 3. The os calcis. 4. The scaphoid bone. 5. The in- 

 ternal cuneiform bone. 6. The middle cuneiform bone. 7. The external cuneiform 

 bone. 8. The cuboid bone. 9. The metatarsal bones of the first and second toes. 10. 

 The first phalanx of the great toe. 11. The second phalanx of the great toe. 12. The 

 first phalanx of the second toe. 13. Its second phalanx. 14. Its third phalanx. 



