14 THE SURGICAL ANATOMY OF THE HORSE 



behind. It arises from the external lateral ligament of the elbow, from 

 the outer side of the upper end and outer border of the radius, and from 

 the line of junction of the radius and ulna. 



Its thin muscular portion is followed by a tendon which plays 

 through the vertical groove on the outer aspect of the inferior extremity 

 of the radius. It then crosses the outer side of the knee, passing 

 through a synovial sheath. From the fibrous arch of the knee it 

 receives a reinforcing band, and is joined by the portion of the tendon 

 of the extensor pedis already referred to. It runs down the limb parallel 

 to the extensor pedis, and is inserted into the upper extremity of the 

 anterior face of the os sufFraginis. 



This muscle extends the knee and fetlock, and is also supplied by the 

 musculo-spiral nerve. 



The Extensor Metacarpi Obliquus (24). — This is a small muscle which 

 arises from the inferior portion of the outer aspect of the radius. At 

 its origin the muscle is broad and flat, and it is here crossed by the 

 extensor pedis. 



Its tendon plays over that of the extensor metacarpi magnus, passes 

 through the oblique groove at the inferior extremity of the radius, and 

 runs downwards and inwards to be inserted into the head of the inner 

 small metacarpal bone. 



Its action is similar to that of extensor metacarpi magnus, 

 and like the latter muscle it is supplied by the musculo-spiral 

 nerve. 



The Flexor Metacarpi Externus (21). — This muscle is placed behind 

 the extensor suffraginis, and arises from the outer condyle of the 

 humerus. Its muscular portion is succeeded by a thick powerful 

 tendon, which splits into two divisions. One of these is inserted into 

 the upper border of the pisiform bone together with the tendon ot 

 insertion of the middle flexor, and the other plays through the groove 

 on the outer aspect of the pisiform bone and is inserted into the head of 

 the outer small metacarpal bone. 



