FLEXOR PERFORATUS AND FLEXOR PERFORANS 125 



may affect one or other of the two tendons, or both may be affected. 

 But when the condition is confined to one tendon the connective tissue 

 between them usually becomes so indurated as to necessitate tenotomy 

 of both. It is most commonly the case that the perforans is originally 

 affected, and that subsequently the connective tissue and the perforatus 

 tendon become implicated. 



When the tendons are retracted the large metacarpal bone becomes 

 altered in position, for instead of being placed almost vertically, it 

 takes a position which is downwards and forwards, and there is partial 

 displacement of its lower articular surface from the upper articular 

 surface of the sufFraginis. This gives us the condition commonly known 

 as Knuckling of the Fetlock, and when this occurs the plantar aspect of 

 the foot usually rests flat upon the ground. 



In chose cases where knuckling does not occur the heel of the foot is 

 drawn upwards so that it does not touch the ground, and the animal 

 walks on its toe. 



As a method of treatment the operation of tenotomy is performed. 

 The seat usually selected is, in the case of the fore limb, the middle third 

 of the metacarpal region and on the inner aspect of the limb. On 

 account of the numerous anatomical structures which are exposed to 

 injury during the course of the operation, it will perhaps be of advantage 

 to study the dissected seat before proceeding further. Such a dissection 

 is illustrated in Plate V., from which it will be seen that the perforatus 

 tendon is placed immediately behind the perforans and closely applied 

 to it. Running along the inner edge of the perforans tendon is the 

 internal plantar nerve, which gives off the branch by which it communi- 

 cates with the external plantar nerve, just above the position where we 

 shall make our incision. In front of the nerve the large metacarpal artery 

 is placed, and iw front of this again is the internal metacarpal vein, which 

 runs upwards along the edge of the suspensory ligament. Extending 

 upwards from the fetlock and enveloping the tendons is the great 

 sesamoidean synovial sheath (Plate XXVII.) , and extending downwards 



