140 MUSCULAR SYSTEM. 



Relaiions. — Anteriorly, with the faschia and skin ; posteriorly, 

 with the radius : externally, with the extensores pedis et obli- 

 quus ; internally, with the flexor brachii and the skin. The su- 

 perficial brachial vein ascends along its inner side. 



Structure. — Its superior attachment is principally fleshy ; 

 though it possesses some tendinous fibres which are inseparably 

 united with the tendon of the next (to be described) muscle. 

 The middle part has but few tendinous intersections. The sur- 

 faces are partly aponeurotic. Below the middle of its length 

 arises a tendon, round at its origin, but gradually growing flat, 

 and expanding in breadth towards its termination : it passes, at 

 the knee, under the anterior annular ligament, within a synovial 

 sheath, furnished with a bursa mucosa. 



Jction. — To extend the leg. 



EXTENSOR PEDIS. — Epilroch lo-p repha langeus. 



Situation. — Fore and outer part of the arm. 



Form. — Elongated ; pyramidal : more flattened than, but not 

 so thick as, the preceding muscle. 



Attachment. — Superiorly, to the fore part of the external con- 

 dyle of the humerus, to the outer part of the head and superior 

 external part of the body of the radius, and also to the capsular 

 ligament of the elbow joint : inferiorly, to the front parts of the 

 lower end of the os suffraginis, the os coronas, and the coronal 

 process of the os pedis ; adhering in its course to the capsular 

 ligament of the fetlock joint. 



Relations. — Anteriorly, with the faschia and skin : posteriorly, 

 with the extensor obliquus and the radius : internally, with the 

 preceding muscle : postero-externally, with the extensor suff'ragi- 

 nis. Behind it, between the bone and it, run branches from the 

 spiral artery and nerve. 



Structure. — The superior attachment is both tendinous and 

 fleshy : that portion which is attached to the radius consists of a 

 broad, thin, pale, fleshy fasciculus, running to unite itself to the 

 main body of the muscle. It has but one or two, and those but 

 partial, tendinous intersections. Its surfaces are aponeurotic. It 

 becomes a single tendon nearly about the same place as the for- 

 mer muscle ; but the tendon is smaller. It pursues its course 

 under the annular ligament, through a cellular sheath furnished 

 with a bursa ; and continues down the leg, closely attached by 

 cellular membrane to the cannon bone, broadening somewhat 

 in its course, but widely expanding after it has passed over the 

 fetlock; and in its expansion so completely covering and ad- 

 hering to the pastern joints, that it seems to them, in front, to 

 serve the purpose of capsular ligament. 



