102 OSTEOLOGY 



surface is convex and just beneath the skin. The outer 

 surface of the malleolus is smooth and articulates with 

 the astragalus bone. The posterior surface is flattened 

 and crossed by the flexor tendons of the toes and the 

 tibialis posticus muscle. 



The Fibula. The fibula (clasp) or peroneal bone, 

 nearly equal in length to the tibia, is the thinnest long 

 bone in the body. It lies parallel with the tibia at the 

 outer side of the leg. It articulates by its upper ex- 

 tremity with the outer tuberosity of the tibia, by its 

 lower extremity with the astragalus. The two articu- 

 lating extremities are held in place by ligaments, all 

 entering into the formation of the superior and infe- 

 rior tibiofibular articulation. The inner border has 

 attached to it the outer edge of the interosseous mem- 

 brane, stretching between the titya and fibula. The 

 fibula is the most irregular bone in the body as its 

 surfaces and borders are not evenly defined. 



The outer aspect of the lower extremity is subcuta- 

 neous and is grooved behind for the lodgement of the 

 tendons of the peroneus longus and brevis muscles 

 the latter tendon being next to the bone. The lower 

 extremity forms the external malleolus. 



The Bones of the Foot. The bones of the foot con- 

 sist of three divisions the tarsus, metatarsus, and 

 phalanges (toes). 



The Tarsus. This consists of seven irregular-shaped 

 bones held in position by ligaments and reinforced by 

 the inserted sheaths of the tendons of muscles. The 

 bones are, viz., the os calcis or calcaneum, astragalus, 

 cuboid, scaphoid, internal, middle, and external cuneiform. 

 The os calcis forms the heel, and is the largest of the 

 seven bones. It articulates above, with the astragalus; 

 in front, with the cuboid. It presents six surfaces 

 superior, inferior, internal, external, anterior, and pos- 

 terior. 



The astragalus or ankle bone (talus) receives the 

 weight of the body from the leg. It articulates with 



