100 



FIBULA. 



Fig. 44.* 



The lower extremity is flattened from without inwards, and pro- 

 longed downwards beyond the articular surface of the tibia, forming 

 the external malleolus. Its external side presents a rough and tri- 

 angular surface, which is subcutaneous. Upon the internal surface is 

 a smooth triangular facet, to articulate with the astragalus ; and a 

 rough depression, for the attachment of the interosseous ligament. The 

 anterior border is thin and sharp ; and the posterior, broad and grooved, 

 for the tendons of the peronei muscles. 



To place the bone in its proper position, 

 and ascertain to which leg it belongs, let 

 the inferior or flattened extremity be di- 

 rected downwards, and the narrow border 

 of the malleolus forwards ; the triangular 

 subcutaneous surface will then point to the 

 side corresponding with the limb of which 

 the bone should form a part. 



The shaft of the fibula is prismoid, 

 and presents three surfaces ; external, in- 

 ternal, and posterior ; and three borders. 

 The external surface is the broadest of the 

 three ; it commences upon the anterior 

 part of the bone above, and curves around 

 it so as to terminate upon its posterior side 

 below. This surface is completely occu- 

 pied by the two peronei muscles. The 

 internal surface commences on the side of 

 the superior articular surface, and termi- 

 nates below, by narrowing to a ridge, 

 which is continuous with the anterior bor- 

 der of the malleolus. It is marked along 

 its middle by the interosseous ridge, which 

 is lost above and below in the inner bor- 

 der of the bone. The posterior surface is 

 twisted like the external, it commences 

 above on the posterior side of the bone, 

 and terminates below on its internal side ; 

 at about the middle of this surface is the 

 nutritious foramen, which is directed down- 

 wards. 



The internal border commences superior- 

 ly in common with the interosseous ridge, 

 and bifurcates inferiorly into two lines, 



* The tibia and fibula of the right leg articulated and seen from behind. 1. 

 The articular depression for the external condyle of the femur. 2. The articular 

 depression for the internal condyle ; the prominence between the two numbers 

 is the spinpus process. 3. The fossa and groove for the insertion of the tendon 

 of the semi-membranosus muscle. 4. The popliteal plane, for the support of 

 the popliteus muscle. 5. The popliteal line. 6. The nutritious foramen. 7. 



! 



