154 THE SURGICAL ANATOMY OF THE HORSE 



cutaneous filaments of this nerve which were distributed over the area of 

 the affection. 



In performing the operation of ulnar neurectomy the seat of opera- 

 tion is situate very slightly to the outer side of the middle line on the 

 posterior aspect of the limb, and about three inches above the ridge of 

 the pisiform bone. 



The depression between the tendons of the flexor metacarpi externus 

 and flexor metacarpi medius muscles, which has already been referred to 

 in the superficial examination, should be carefully located (Plate XXXI.), 

 and after the usual preliminary preparation a vertical incision about an 

 inch and a half in length should be made in this depression, cutting 

 through the skin and subcutaneous fascia. 



Upon separating the edges of the cutaneous wound a dense layer of 

 deep fascia will be seen connecting the tendons of the metacarpal liexors 

 on their posterior aspects. Another incision, corresponding in position 

 and direction to the cutaneous one already made, should be made through 

 the fascia (Plate XXXII.). 



The edges of the deep incision should now be separated, when the 

 nerve will usually be found immediately in front of the operator's line of 

 vision and placed between the tendons. Occasionally, however, it may 

 not be seen in this situation, and in these cases it will usually be found 

 on the anterior surface of the tendon of the flexor metacarpi medius. 



The tenaculum should be passed beneath the nerve, and the with- 

 drawal of the nerve through the cutaneous opening will be facilitated 

 by slightly flexing the knee. 



THE MEDIAN NERVE 



This nerve, which is the largest of the nerves given off from the 

 brachial plexus, derives its fibres from the inferior primary divisions of 

 the fifth, sixth, seventh, and eighth cervical and the first dorsal nerves. 



