THE POSTERIOR LIMBS. 



103 



Fig. 65. 



calcaneus, between the tibia and the scaphoid, and divided intone faces : 



1, A superior and anterior, formed as an 

 articular pulley to correspond to the in- 

 ferior extremity of the tibia; this pulley, 

 oblique from above downwards, forwards, 

 and outwards, may be considered as the 

 type of the most perfect trochlea in the 

 organism; its groove receives the median 

 tenon of the tibia, and its two ridges or lips 

 fit into the lateral furrows of that bone. 



2, An inferior face, occupied by a slightly 

 convex articular surface responding to the 

 scaphoid ; this surface is notched outwardly 

 by an excavation for ligamentous insertion. 



3, A posterior face, irregular, cut into three 

 or four diarthrodial facets adapted for 

 similar facets on the calcaneus, and which 

 are separated by a wide, rugged excavation. 



4, An external face, covered with imprints. 



5, An internal face, provided below with 

 a small tubercle of insertion. 



Calcaneus. A bone vertically elongated, 

 flattened on both sides, and presenting two 

 faces, two borders, and two extremities. 



The external face is smooth and nearly 

 plane. The internal face is excavated into 

 a gliding groove to form the tarsal arch, in 

 which passes the tendon of the perforans. 

 The anterior border is slightly concave. 

 The posterior border is thicker, straight, 

 and rugged. The superior extremity, 

 slightly tuberous, constitutes the summit 

 of the calcaneus, and is divided into three 

 parts : a middle, which gives attachment to 

 the tendon of the gastrocnemius ; the other, 

 the anterior, is a smooth surface on which 

 this tendon rests when the foot is much 

 flexed ; the third, altogether posterior, also 

 constitutes a gliding surface for the tendon 

 of the perforatus. The inferior extremity, 

 wide and voluminous, shows in front three 

 or four articular facets which correspond 

 to the astragalus, and are separated, like 

 those of the last bone, by an irregular and 

 slightly excavated surface of insertion. 

 Below, it shows for articulation with the 

 cuboid a fifth facet, continuous with ono of 

 the preceding. 



Development. The calcaneus is deve- 



10, besamoid bones ; 11, Coronary, , a _ - * i-j? *. , ^f 



second, or middle phalanx: 12, lo P ed from two nuclel of ossification, one ^ 



LEFT HIND FOOT; EXTERNAL 

 ASPECT. 



1, Tibia; 2, Summit of calcis or cal- 

 caneus ; 3, Astragalus ; 4, Cuboid ; 

 5, Scaphoid; 6, Cuneiform mag- 

 num ; 7, Large metatarsal bone ; 

 8, Small metatarsal bone; 9, Suf- 

 fraginis, proximal, or first phalanx ; 



Pedal bone, or third or distal 

 phalanx ; 14, Navicular bone ; 15, 

 Basilar process of pedal bone. 



which is for the summit. 



Cuboid bone. This little bone, situated 

 a t the external side of the scaphoid and the 



