224 MYOLOGY. 



Origin. — The fleshy part arises from the base of the epitrochlea^ 

 and the anterior border of the external lateral ligament of the 

 elbow joint, the front of the distal extremity of the humerus, and 

 the outer part of the head of the radius. The tendon, which is 

 double, passes through a synovial theca in the external groove on 

 the distal end of the radius, under the anterior annular ligament. 

 Below the knee it sends a small tendon to join that of the 

 extensor suffraginis ; then expanding, it passes over the front of 

 the fetlock joint, being attached to the capsular ligament, and 

 having a small synovial bursa interposed ; below the fetlock it 

 receives on either side a strong slip from the suspensory ligament, 

 and it becomes attached to the anterior part of the first and 

 second phalanges. 



Insertion. — To the pyramidal process of the os pedis. 



Relation. — Anteriorly and externally it is covered by the 

 fascia ; posteriorly related with the extensor suffraginis, the 

 radius, carpus, metacarpus, and phalanges ; internally with the 

 extensor metacarpi magnus. 



Action. — To extend the phalanges on each other, and assist 

 in extending the carpus. 



If the tendon which joins that of the extensor suffraginis be 

 carefully traced upwards, it will be found to be continuous with 

 a long thin muscle separable from the extensor pedis, and placed 

 along its postero-extemal aspect ; it arises from the external 

 lateral ligament of the elbow joint and the corresponding tuber- 

 osity pf the radius, and has received the name of Phillips' muscle 

 (Fig. 80. h). Somewhat anteriorly to the above a still smaller 

 muscle may be found arising from the external arciform ligament, 

 and terminating in a small tendon, which joins that of the 

 extensor pedis a short distance above the carpus ; this has been 

 called Thiernesse's muscle (Fig. 80. g). These two muscles are 

 not generally described, but are regarded as forming a part of 

 the extensor pedis. 



EXTENSOR SUFFRAGINIS. 



(Eadio-prephalangetis.) 



(Fig. 78. 1.) 



Situated on the external part of the fore-arm, between th» 



extensor pedis and the flexor metacarpi externus, this muscle is 



semipenniform, consisting of a flattened fleshy belly, enveloped in 



