DISSECTION OF THE POSTERIOR LIMB. 73 



The SoLEDs (Plate 18). In some veterinary text-books this muscle 

 is erroneously termed plantaris. It is a small muscle of delicate 

 texture, and is often partially or entirely removed in cleaning the 

 gastrocnemius. It arises from the head of the fibula, and its tendon joins 

 that of the preceding muscle, which it assists in extending the hook. 



Directions. — The inner head of the gastrocnemius is to be severed at 

 its origin, and turned downwards in the manner shown in Plate 17. 



The Superficial Flexor of the digit (flexor perforatus) (Plates 17 

 and 18) is remarkable in that, • throughout nearly the whole of its 

 extent, it exists as a strong tendinous cord with a sparing admixture 

 of muscular fibres in its upper fifth only. It arises from the bottom 

 of the supracondyloid fossa ; and, winding round the gastrocnemius 

 tendon in the manner already described, it gains the summit of the 

 OS calcis, over the posterior portion of which it plays by means of 

 a synovial bursa. At the os calcis it detaches on each side a slip 

 to be inserted into the bone. It is continued downwards in the 

 metatarsal and digital regions in the same manner as the perforatus 

 of the fore limb, becoming finally inserted by a bifid termination 

 into the second phalanx. In front of the tendons of the superficial 

 flexor and gastrocnemius there will be noticed a strong fibrous band, 

 which is united to these muscles above, and inserted into the os 

 calcis below, while laterally it is continuous with the deep fascia of 

 the leg. 



Action. — It flexes successively the pastern and fetlock joints ; and, by 

 its insertion into the os calcis, it is also an extensor of the hook-joint. 

 It also plays an important part in mechanically maintaining the hock in 

 a state of extension so long as the hip and stifle joints are kept extended 

 by muscular contraction. 



The flexor perforatus of the horse is represented in man by two 

 distinct muscles — the plantaris and the Jlexor hrevis digitm-iim. 



Directions. — The deep layer of muscles at the back of the leg consists 

 of the popliteus, the flexor perforans, and the flexor acoessorius ; and 

 these should now be examined as far as possible without disturbance of 

 the vessels and nerves. The superficial muscles must therefore, in the 

 meantime, be allowed to remain in position. 



The Popliteus (Plate 17). This muscle is placed immediately behind 

 the stifle-joint, whose posterior ligament it covers. It arises by a tendon 

 from the lower and most anterior of the two pits situated on the outer 

 side of the external condyle of the femur. (The other pit is for the 

 attachment of the external lateral ligament of the stifle, the ligament 

 concealing the origin of the tendon.) The tendon is partly invested by 

 the synovial membrane of the joint, and plays round the external serai- 

 lunar cartilage, and over the articular surface of the tibia. The fibres 

 of the muscle have an oblique direction downwards and inwards, and are 



