S3 THE HUMAN BODY. 



of the sesamoid bones, which adapts itself by two articular 

 facets to those presented by the condyles of the femur, and 

 gives attachment by its upper border to the tendon of the 

 extensors of the leg, while by its lower border it is intimately 

 united to the ligament of the knee-pan, which fastens it to 

 the tibia. In comparing the elbow with the knee, we per- 

 ceive the striking similarity of the knee-pan to the olecranon. 

 The knee-pan serves as a pulley for the extensor-muscles, the 

 action of which upon the leg is increased by the change of 

 direction given to them, while the olecranon is a powerful 

 lever, by means of which the fore-arm is extended. 



Fig. 17. Knee-joint. 



Front view. Side view. 



A. Femur. A. Femur. 



D, t>. Condyles of femur. B. Knee-pan. 



d. Upper extremity of fibula. C. Tibia. 



C. Tibia. D. Fibula. 



D. Fibula. 



The second bone of the leg is \hefibula, which is parallel 

 to the tibia, and with it forms the articulation of the foot. 

 This bone, which takes no part in the articulation of the 

 knee, yet represents the ulna, which plays so important a 

 part in the formation of the elbow, while the tibia corre- 



