24 THE SURGICAL ANATOMY OF THE HORSE 



well-defined muscular portion, and this in turn is followed by a long 

 tendon of insertion. 



The latter tendon is observed to disappear at the tarsus, on the 

 inner side of which it plays through a synovial passage. It leaves this 

 tube and unites with the tendon of the flexor perforans immediately 

 below the hock, the position where they unite being just visible in the 

 Plate. 



The flexor accessorius assists the flexor perforans, and is supplied by 

 the internal popliteal nerve. 



The Flexor Perforans (19). — A portion of this muscle is represented, 

 namely, that part which arises from the vertical ridges on the back of the 

 tibia, below the insertion of the popliteus. Along this part of the 

 muscle the tendon of the flexor accessorius runs. 



The tendon of the perforans plays through the tarsal sheath and runs 

 down the limb in 'the manner already described, being related to the 

 corresponding vessels and nerves on this aspect of the limb. 



The Perforatus Tendon (30) is better defined than in the Plates repre- 

 senting the outer aspect, and the resumption of its relationship behind 

 that of the perforans, after the latter has left the tarsal sheath, is evident. 



THE BLOOD-VESSELS 

 The Arteries 



The Posterior Tibial Artery (16). — This vessel is one of the terminal 

 divisions of the popliteal artery, which splits up into the anterior and 

 posterior tibial vessels just below the stifle. It is much the smaller of 

 the two branches. The larger branch — the anterior tibial artery — passes 

 forwards through the tibio-fibular arch, and runs down the front of the 

 tibia beneath the flexor metatarsi muscle. It is therefore deeply seated, 

 and is in consequence not represented in the preceding Plate. At the 

 tarsus it divides into the perforating tarsal and large metatarsal arteries, the 



