222 MYOLOGY. 



two distinct groups, the anterior and posterior, the first of which 

 are all extensors, the second all flexors. All these muscles are 

 inserted below the radius, and therefore act upon the carpus 

 or on the joints below. The region is enclosed in the antibrachial 

 fascia, an exceedingly strong covering, which is firmly attached 

 to the radius and ulna. 



Anterior Antibrachial Group, 

 extensors. 

 The extensor group includes four muscles : — 



Extensor metacarpi magnus. 

 Extensor metacarpi obliquus. 



Extensor pedis. 

 Extensor suffraginis. 



EXTENSOR METACARPI MAGNUS, 



{Epicondylo-premeiacarpeus.) 



(Fig. 78. g.) 



Situated in front of the radius, and in figure pyramidal, extend- 

 ing downwards, it consists of a fleshy belly, and a long flat tendon, 

 which commences at about the lower third of the radius, and passes 

 over the carpus, terminating at the head of the metacarpus. 



Origin. — From the epitrochlea, or ridge above the external 

 condyle of the humerus, from the capsular ligament of the elbow 

 joint anteriorly, and the surface just above. It receives a strong 

 tendinous band from the flexor brachii. The tendon passes 

 through a groove or theca in the anterior part of the distal end of 

 the radius, where there is a synovial sheath or bursa, then over 

 the knee through a second synovial apparatus. Two synovial 

 sheaths are thus interposed betv/een the bones and the tendon, 

 the latter being bound down by the anterior annular ligaments, 

 and by the tendon of the extensor metacarpi obliquus, which 

 crosses it in an oblique manner just above the carpus. 



Insertion. — To a tuberosity on the anterior part of the head 

 of the great metacarpal bone, towards its inner side. 



Relation. — Anteriorly with the fascia ; posteriorly with the 

 radius ; externally with the extensor pedis ; supero-internally with 

 the humeralis obliquus and flexor brachii ; inferiorly with the 

 extensor obliquus. 



Action, — To extend the carpus. 



r- 



