OSTEOLOGY. 67 



The inferior extremity, smaller than the superior, is quadri- 

 lateral, and presents in front a smooth surface for extensor ten- 

 dons, behind a groove for flexor longus pollicis tendon, externally, 

 a rough, triangular, articular surface, for fibula, and internally 



The internal malleolu*. which projects downward, and ar- 

 ticulates by its outer surface with the astragalus. 



Its inner surface is smooth and subcutaneous; its posterior 

 border is grooved for the tendons of the tibialis posticus and 

 flexor longus digitorum muscles, and to its tip is attached the in- 

 ternal lateral ligament. 



It articulates with three bones femur, fibula, and astraga- 

 lus. 



Its muscular attachments are twelve ligamentum patellae, 

 popliteus, soleus, flexor longus digitorum, tibialis posticus, senri- 

 membranosus and tendinosus, gracilis, sartorius, tibialis anticus, 

 and extensor longus digitorum, biceps. 



It is developed from three ossific centres, one each for shaft, 

 upper and lower extremities. 



THE FIBULA, or peroneal bone, is a long, slender bone on the 

 outer aspect of the leg, and consists of a shaft, upper and lower 

 extremity. 



The shaft is prismoidal, four-sided, twisted on itself, and 

 arched backward. Its antero-internal border, or interosseous 

 ridge, gives attachment to the interosseous membrane. The 

 postero-internal border, called also oblique line, and the other 

 surfaces and borders give attachment to all the muscles except the 

 biceps. 



Nutrient foramen, about the middle of the anterior internal 

 surface, is directed downward. 



The superior extremity presents a neck, supporting a 

 rounded, irregular head, which articulates by a flattened facet on 

 itvS inner surface with the tibia, and is prolonged upward on its 

 outer side by the styloid process, giving attachment to the biceps 

 tendon and the external lateral ligament of the knee. 



The inferior extremity expands into the external malleolus, 

 with its convex internal surface for articulation with astragalus, 

 outer convex surface subcutaneous, and posterior border deeply 

 ijniorcd lor tendons of peroneus longus and brevis muscles. 



To the sum mil is attached the middle fasciculus of the ex- 

 ternal lateral ligament, and to rough dc/i regions in front and 

 behind the anterior and posterior fasciculi. 



It articulates with two bones, tibia and astragalus. 



Its muscular attachments are nine soleus, biceps, three 

 peronri. tibialis posticus, flexor longus pollicis, and extensor 

 longus digitorum and pollicis. 



