THE BONE.S OF THE LOWER LIMB. 



INTEROSSEOUS 



INFERIOR 



WTEBOSSEOUSx 



LIGAMENT 



ASTRA.OALUS- 



Fig. 143. RIGHT FIBULA : INNER 

 VIKW. (Drawn by T. W. P. 

 Lawrence. ) 



by the tendons of the peroneus longus and brevis 

 muscles : externally it is convex and subcutaneous ; 

 and a triangular subcutaneous surface is continued 

 up from it for two or three inches on the shaft. 



The shaft has four surfaces, separated by as 

 many prominent lines. Three of these lines are 

 known as borders, the fourth is the interosseous 

 ridge. The anterior border is the most prominent ; 

 it commences at the fore part of the neck, and 

 takes a straight course down the front of the bone 

 as far as the lower fifth, where it bifurcates, the 

 one line running to the front of the malleolus, the 

 other to the back, and enclosing between them the 

 triangular subcutaneous surface. Immediately in- 

 ternal to this is the interosseous ridge, so named 

 from giving attachment to the interosseous mem- 

 brane ; it is close to the anterior border above, 

 but gradually diverges from that as it passes 

 downwards ; it terminates about an inch and a 

 half above the ankle-joint in the apex of a tri- 

 angular surface, convex and roughened by the 

 inferior interosseous ligament, fixing it to the tibia. 

 The external border extends the whole length of 

 the bone, from the styloid process to the back of 

 the malleolus, inclining inwards in its lower half. 

 The remaining border, internal, commences at the 

 inner side of the neck, runs down the shaft for 

 two-thirds of its length, and then ends by joining 

 the interosseous ridge. The surfaces are : the 

 anterior, between the anterior border and the in- 

 terosseous ridge, narrow above, wider below ; it 

 gives origin to the extensor muscles of the toes 

 and the peroneus tertius : the external, broadest of 

 all, somewhat hollowed at the upper part, and 

 turning below to the back of the malleolus, thus 

 indicating the course of the peronei muscles, by 

 which it is completely covered : the posterior, which 

 winds to the inner side of the bone in its lower 

 half ; in its upper third it is rough, giving origin 

 to the soleus, while the rest of its extent is occupied 

 by the flexor longus hallucis : and the internal, 

 between the internal border and the interosseous 

 line, a fusiform surface over the upper two-thirds 

 only of the shaft, and giving origin to the tibialis 

 posticus ; it is often traversed by an oblique ridge 

 which gives attachment to a tendinous septum in 

 the muscle. The foramen of the medullary artery 

 is small, placed on the internal or posterior surface, 

 about the middle, and is directed downwards. 



The head of the fibula projects under the skin 

 at the outer and back part of the knee, behind and 

 somewhat below the level of the prominent outer 



