140 PRACTICAL ANATOMY. 



external surface, and an articular end. The anterior sur- 

 face, over which the extensor tendons pass, is slightly con- 

 cave and smooth ; the posterior surface presents the 

 grooves for the tibialis posticus, flexor longus digitorum, 

 and flexor longus pollicis. The external surface, convex 

 from before backward, is continued downward as a quad- 

 rangular process of bone, called the inner malleolus, which 

 projects about three-fourths of an inch below the articular 

 surface for the upper surface of the astragalus. On the 

 outer side of the internal malleolus is the articular surface 

 for the inner side of the astragalus. Thp paternal pyvfacp 



pTMAT^fj n.irigngnTjpr nrtinnlgv a^rflapp for flip fihnla. The 



inferior surface presents a trilateral articular surface for 

 the astragalus, it is broad externally, smaller where it 

 becomes continuous with the articular surface of the 

 outer side of the inner malleolus. 



In structure, the tibia presents a bulky head made of 

 a shell of dense bone, inclosing a large quantity of can- 

 cellous tissue, arranged so as to present many large 

 alveolar spaces. The lamellae of the cancellous tissue 

 are strong and thick, although short, and frequently pre- 

 sent the Haversian system of canals. The bone de- 

 velops by four centres, one for the shaft, one for the 

 upper extremity, one for the lower extremity, and one 

 for the malleolar process. 



THEJ3BCLA, OR SPLINT-BONE. 



The fibula, or splint-bone, is the outer bone of the leg. 

 TMs. lon and slpnfWj ^n^Mpelonffs to the class of long 

 bones. It presents a shaft, upper extremity, or head, and 

 lower extremity, or outer malleolus. The shaft is pris- 

 moid, slightly twisted, and presents a well-marked inner 

 border for attachment of the interosseous ligament. The 

 posterior border is well-marked; the anterior border is 



