356 THE INFERIOR EXTREMITY 



facilitated by the presence of a common mucous sheath. On 

 the lateral surface of the calcaneus the tendons are retained 

 in position by the inferior peroneal retinaculum, but each tendon 

 lies in a separate compartment surrounded by its own special 

 prolongation of the mucous sheath. At the back of the 

 lateral malleolus, the tendon of the peronaeus brevis is 

 anterior to the tendon of the peronaeus longus and therefore 

 between it and the fibula, consequently as the two tendons 

 turn forwards along the lateral side of the calcaneus the 

 tendon of the peronoeus brevis occupies a higher position 

 than the tendon of the peronaeus longus and passes above 

 the trochlear process of the calcaneus, which intervenes 

 between the mucous sheaths of the two tendons. The 

 peronaeus brevis is supplied by the superficial peroneal nerve. 

 It is a plantar flexor and an evertor of the foot. 



N. Peronaeus Communis (O.T. External Popliteal Nerve). 

 The common peroneal nerve has previously been traced as 

 far as the neck of the fibula. At that point it disappears 

 from view by passing forwards between the peronaeus longus 

 muscle and the bone. The muscle must therefore be care- 

 fully turned aside from its origin in order that the nerve may 

 be followed to its termination. As it lies between the peronaeus 

 longus and the neck of the fibula it gives off a small 

 recurrent articular branch to the knee joint, and then divides 

 into the deep and superficial peroneal nerves. 



The recurrent branch pierces the extensor digitorum longus, 

 and then accompanies theanterior tibial recurrent artery through 

 the upper fibres of the tibialis anterior. It gives twigs to 

 the tibialis anterior, but its terminal filaments are distributed 

 to the synovial stratum of the capsule of the knee joint. 



The deep peroneal nerve pierces the proximal part of the 

 extensor digitorum longus to reach the anterior region of the 

 leg, where it has already been dissected. 



N. Peronseus Superficialis (O.T. Musculo-Cutaneous Nerve). 

 The superficial peroneal nerve passes distally in the sub- 

 stance of the peronaeus longus ; reaches the interval between 

 the two peronaei muscles ; gives branches to both ; and 

 then lies between the peronaeus brevis and the extensor 

 digitorum longus. In the distal third of the leg it pierces the 

 deep fascia, becomes cutaneous, and divides into a medial 

 and a lateral branch, which have been called the medial and 

 intermediate dorsal cutaneous nerves of the foot (p. 338). 



