252 



COMPARATIVE ANATOMY 



femur to the foot. Two flattened condyles articulate with the femur. 

 The ligament of the patella is attached to the ventral surface of the upper 

 extremity of the tibia. The shaft of the tibia is triangular having an 

 anterior sharp crest from which the tibialis anterior muscle has its origin. 

 The lower extremity of the tibia is smaller than the upper. Articulation 



Fig. 209. — Stages in the development of the extremities in mammals. (Redrawn 

 after Bardeen, Lewis and Corning.) A is a cross section of a monkey embryo showing 

 an arm bud. (Redrawn from Arey after KoUman.) 5 is a seven-week human embryo 

 in left lateral aspect. (Redrawn after Corning.) C is an eight-week human embryo in 

 left lateral aspect. (Redrawn after Corning.) Z? is a nine-week human embryo in left 

 lateral view. 



is with the talus bone of the ankle. The large process of the medial 

 malleolus extends from its lower outer border. (Fig. 206) 



The Fibula. The fibula is the slenderest of the long bones. It func- 

 tions chiefly as a basis of attachment of leg muscles which serve as 

 extensors and flexors of the toes. Its upper extremity articulates with 

 the tibia, its lower is prolonged into a conspicuous lateral malleolus. 



The Tarsus. The tarsal or ankle bones number seven. The proximal 

 tarsals are the talus and calcaneus. Three ctmeiform bones and a cuboid 

 form the distal tarsals. Between the two on the inner side of the instep 



