i6 THE SURGICAL ANATOMY OF THE HORSE 



the tibia, from the head of the fibula, and from the tibio-fibular inter- 

 osseous membrane. 



The muscular portion keeps in close relationship to the peroneus 

 throughout its course, and its tendon disappears through the tarsal 

 sheath, where it glides over the supero-posterior aspect of the body of 

 the calcis to the inner side of the tuber. The tendon again makes its 

 appearance below the hock as it leaves the sheath. It is plainly 

 visible owing to the slight displacement of the tendon of the per- 

 foratus (28), It continues its course down the limb between the 

 suspensory ligament in front and the perforatus tendon behind, and 

 along its edges run the plantar nerves and vessels. It next plays 

 through the ring formed by the perforatus, leaves the ring below the 

 fetlock, and becomes ultimately inserted into the semilunar crest of the 

 pedal bone. 



The perforans is an extensor of the hock and a flexor of the fetlock, 

 pastern, and corono-pedal joints. It is supplied by the internal popliteal 

 nerve. 



The Peroneus Muscle (18). — This muscle arises from the external 

 lateral ligament of the stifle, from the outer tuberosity of the tibia, and 

 from the head of the fibula. The tendon of origin is plainly visible, 

 and is succeeded by a well-defined elongated muscular belly, which is 

 represented throughout its extent. Its inferior tendon commences above 

 the hock. It then passes along the groove on the external malleolus, 

 over the large metatarsal artery, and under the most inferior of the 

 three annular bands to become united to the tendon of the extensor 

 pedis from three to four inches below the hock (23). 



The peroneus muscle assists the extensor pedis, and is supplied by the 

 musculo-cutaneous division of the external popliteal nerve. 



The Extensor Pedis (11). — This muscle is also represented from its 

 origin to its insertion : it arises in common with the tendinous division 

 of the flexor metatarsi from the pit which is placed between the external 

 femoral condyle and the outer lip of the trochlea. 



