222 MYOLOGY. 



divided into 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 pedis. 



Extensor metacarpi obliquus. Extensor suffraginis. 



EXTENSOR METACARPI MAGNUS. 



(Epicondylo-premetacarpeus. ) 



(Fio. 78. g.) 



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

 extending 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 tbeca 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 

 syuovial sheaths are thus interposed between 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. 



