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SUPERFICIAL DISSECTIONS 13 



pedis, forms the bulging mass in front of the forearm, which is so 

 distinctly visible in the living animal. 



It arises from the roughened ridge above the external condyle of the 

 humerus, and its muscular portion gradually tapers as we descend to 

 within two or three inches of the knee, where it is succeeded by a 

 tendon. The latter passes under the extensor metacarpi obliquus and 

 through the middle groove on the front of the lower extremity of the 

 radius. It next crosses the knee in a vertical direction, where it lies on 

 the anterior common ligament, and runs to its insertion into a roughened 

 area at the front of the upper extremity of the large metacarpal bone. 

 This muscle is the principal extensor of the knee joint, and its nerve 

 supply is derived from the musculo-spiral. 



The Extensor Pedis (22). — This is placed behind the extensor meta- 

 carpi magnus. It arises trom the small depression which is placed to the b 

 outer side of the coronoid fossa, from the external lateral ligament of the r^ 

 elbow and from the upper portion of the outer aspect of the radius. ij 



Its muscular portion tapers at both ends, and inferiorly it is succeeded ^■ 

 by a tendon which plays over the broad origin of the extensor metacarpi ^ 

 obliquus. It next passes through the outer of the two vertical grooves T 

 on the front of the radius, and crosses the knee under the annular band -^ 

 of fascia, being superficially placed to the anterior common ligament. r> 



The tendon is divisible into two portions — the outer and smaller of 

 which joins the tendon of the extensor suffraginis. The inner and larger 

 tendon plays over the fetlock and pastern joints and takes the place of an 

 anterior common ligament of the latter, the synovial membrane of the 

 pastern joint being supported by the posterior face of the tendon. The 

 tendon then receives the two divisions of the suspensory ligament, and 

 becomes inserted into the pyramidal process of the pedal bone. This 

 muscle extends the knee, fetlock, and inter-phalangeal joints, and is 

 supplied by the musculo-spiral nerve. 



The Extensor Sujfraginis (25). — This is a small muscle which is placed 

 between the extensor pedis in front and the flexor metacarpi externus 



