252 A MANUAL OF ANATOMY 



the posterior margin, external to the peroneal groove. These two 

 divisions enclose between them a triangular area which is continuous 

 with the outer surface of the external malleolus. This border gives 

 attachment to the antero-external intermuscular septum. The 

 antero-internal or interosseous harder, which gives attachment to 

 the interosseous membrane, also commences in front of the head, 

 where it is very near to the antero-external border. As it descends 

 it keeps near to that border at first, but beyond the upper third it 

 gradually diverges from it, and on reaching a point about 2 inches 

 above the external malleolus it bifurcates. One division passes to 

 the anterior margin of the malleolus, becoming incorporated with 

 one of the divisions of the antero-external border, whilst the other 

 passes to the posterior margin of the malleolus, internal to the 

 upper end of the peroneal groove. The two divisions, as they 

 diverge, enclose a rough triangular area, which is slightly convex 

 and gives attachment to the inferior interosseous ligament. The 

 postero-internal border commences on the inner side of the head, 

 not far from the antero-internal. It descends in a backwardly- 

 curved manner, gradually leaving the antero-internal border, but 

 subsequently approaching it, until on reaching the junction of the 

 upper two-thirds and lower third it ends by joining it. This border 

 gives attachment to an intermuscular septum, which separates 

 the tibialis posticus from the soleus and flexor longus hallucis. 

 The postero-external border extends from the back of the head to the 

 back of the external malleolus, internal to the peroneal groove, and 

 in its lower part it turns inwards. It gives attachment to the 

 postero-external intermuscular septum. 



The anterior surface is situated between the antero-external and 

 antero-internal or interosseous borders. It is very narrow over 

 about its upper half, but becomes wider below. It gives origin over 

 about its upper three-fourths to the extensor longus digitorum, 

 over its lower fourth (except about i inch below) to the peroneus 

 tertius, and over about its middle two-fourths to the extensor 

 proprius hallucis, which is nearest to the antero-internal border. 

 The internal surface is situated between the antero-internal and 

 postero-internal borders. It is concave and fusiform, being narrow 

 above and below, but wide at the centre, and it gives origin to the 

 tibialis posticus. The posterior surface is limited by the postero- 

 internal and postero-external borders, and in its lower fourth it 

 undergoes a twist, and turns round to become internal. Over its 

 upper third it gives origin to a part of the soleus, and over its lower 

 two-thirds, except the last inch or more, to the flexor longus hallucis. 

 The external surface lies between the antero-external and postero- 

 external borders. It is the broadest, and in muscular subjects is 

 deeply grooved over rather more than its upper half. Inferiorly it 

 undergoes a twist, and turns round to become posterior, where 

 it leads directly to the peroneal groove on the back of the external 

 malleolus. In this manner the two peroneal tendons are guided to 

 this groove. The upper two-thirds of this surface give origin to 



