POSTERIOR ANTIBRACHIAL GROUP 225 



a strong aponeurotic sheatb, and having its edge turned outwards. 

 The belly ends in a round tendon, which passes through a theca 

 in the vertical groove on the external side of the distal end of 

 the radius, and down the external aspect of the carpus, reaching 

 the anterior surface of the large metacarpal boue. 



Origin. — From the external part of the head of the radius, 

 the external lateral ligament of the elbow joint, the shaft of the 

 radius, and the lateral aspect of the ulna. 



Insertion. — To the head of the os sufifraginis, related also with 

 the capsular ligament of the fetlock joint. Below the knee it is 

 joined by two tendinous slips, one from the tendon of the extensor 

 pedis, the other, a species of check ligament, from the trapezium. 



Relation. — Anteriorly with the extensor pedis ; posteriorl}* 

 with the flexor pedis perforatus, the perforans, and flexor meta-- 

 carpi externus ; externally with the fascia. 



Action. — To extend the digit, and assist the extensor pedis. 



Posterior Antibrachial Group. 



FLEXORS. 



This, the flexor group, consists of seven muscles, three flexors 

 of the carpus, and four flexors of the digit : — 



Flexor metacarpi externus. 

 Flexor metacarpi medius. 

 Flexor metacarpi internus. 



Flexor pedis perforatus. 

 Flexor pedis perforans 

 Ulnaris accessorius. 



Radialis accessorius. 



FLEXOR METACARPI EXTERNUS. 



(JUpitrochleo-carpeus. ) 



(Fig. 78. i.) 



Situated on the postero-external aspect of the fore-arm, this 

 muscle is elongated and flattened, the fleshy belly being inter- 

 sected by strong, tendon. 



Origin. — By a very short strong tendon from the summit of 

 the epitrochlea of the humerus, terminating in two tendons ; the 

 anterior, longer, and more delicate, passes through a synovial 

 theca, in a groove on the external surface of the trapezium. 



Insertion. — The anterior tendon goes to the head of the outer 

 splint bone ; the posterior, short and flat, becomes inserted to the 



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