THE LEG 265 



be carried proximally along the plane of this septum. By drawing aside 

 the peronreus tertius muscle,, the perforating branch of the peroneal artery 

 will be seen piercing the interosseous membrane. It is a small artery 

 which descends upon the distal end of the fibula. As the structures in 

 the anterior crural compartment are being exposed and cleaned, the 

 dissector should, at the same time, carry on the dissection of the dorsum of 

 the foot. There the tendons of the muscles on the front of the leg must be 

 followed to their insertions, and the extensor digitorum brevis muscle 

 defined. The dorsalis pedis artery and the deep peroneal nerve should also 

 be followed, and their branches traced to their various destinations. 



M. Tibialis Anterior (O.T. Tibialis Anticus). The tibialis 

 anterior is a powerful muscle, which takes origin from the 

 distal part of the lateral condyle of the tibia, and from the 

 proximal half of the lateral surface of its body (Fig. 96, p. 264). 

 It likewise derives many fibres from the deep fascia which 

 covers it, from the fascial septum between it and the extensor 

 digitorum longus and the portion of the interosseous 

 membrane on which it rests. In other words, it springs from 

 the structures which form the walls of the medial portion of 

 the osteo-fascial compartment in which it lies. 1 A strong 

 tendon issues from its fleshy belly in the distal third of the 

 leg, and this reaches the dorsum of the foot by passing 

 through both the transverse and cruciate ligaments. On 

 the foot it inclines medially, and, turning round the medial 

 margin, gains insertion by two slips into the medial and 

 distal part of the medial cuneiform bone, and into the adjoin- 

 ing part of the base of the first metatarsal bone. The tibialis 

 anterior is supplied by the deep peroneal nerve. 



M. Extensor Digitorum Longus. This muscle arises, for 

 the most part, from the structures which form the lateral 

 portion of the wall of the anterior crural region. Thus it 

 springs from the distal part of the lateral condyle of the 

 tibia, from the head of the fibula, and from the proximal 

 three-fourths of the anterior part of the medial surface of the 

 body of the fibula (Fig. 96, p. 264). It also takes origin from 

 a small portion of the proximal part of the interosseous 

 membrane, the deep investing fascia of the leg, the anterior 

 peroneal septum, and the inter-muscular septum which dips 



1 To understand the attachments of the muscles of the leg, it is necessary 

 to bear in mind that the interosseous membrane, which stretches across the 

 interval between the two bones of the leg, and thus extends the surface of 

 origin for these muscles, is attached to the interosseous crest of the tibia (i.e. 

 between its lateral and posterior surfaces) and to the interosseous crest of the 

 fibula. The interosseous crest of the fibula traverses the medial surface, and 

 divides it into an anterior and a posterior part. The anterior part gives 

 origin to the extensor muscles and the posterior part to the flexor muscles. 



