MUSCULAR SYSTEM. 139 



Attachment. — Superiorly, to the inner side of the body of the 

 humerus, just above its middle : inferiorly, to the inner part of 

 the apex of the olecranon. 



Re/ations. — Externally, with the caput magnum, teres major, 

 and latissimus dorsi ; internally, with the humerus. 



Structure. — Superior attachments, tendinous and fleshy ; sur- 

 faces, slightly aponeurotic ; inferior attachment by a thin flattened 

 tendon. 



Action of the Three Heads (considered as a single muscle,) — 

 To extend the arm. 



A N CO N E us. — Epicoudj/Io-olecrauius. 



Situation. — Occupying the hollow space behind, between the 

 condyles of the humerus. 



Form. — Short, thick, triangular: base turned downward. 



Attachment. — Superiorly, to the infero-posterior parts of the 

 body of the humerus : inferiorly, to the antero-external part of 

 the olecranon and to the capsular ligament of the elbow joint. 



Relations. — Posteriorly, with the triceps ; anteriorly, with the 

 humerus and the elbow joint. 



Action. — To assist the triceps in the extension of the elbow 

 joint ; and to prevent the capsular ligament from being pinched 

 between the bones during that action. 



MUSCLES OF THE ARM AND FORE LEG. 



These muscles may be classed into two sets: those which 

 extend the leg ; viz. the Extensors ; and those that bend it ; viz. 

 the Flexors. They are both included within and firmly bound 

 by the brachial faschia ; from which some fibres belonging to the 

 superficial muscles derive their origin. 



1.— ANTERIOR BRACHIO-CRURAL REGION. 



This region includes all the extensor's. The mass of them 

 forms the prominence so perceptible upon the front of a well- 

 formed arm. Collectively considered, they possess much less 

 power than the flexors. 



EXTENSOR METACARPi MAGNUS. — Epitrochlo-prcmetacarpeus. 



Situation. — Fore" part of the arm. 



Figure. — Pyramidal : rounded superiorly ; flattened inferiorly. 



Attachment. — Superiorly, to the outer and fore parts of the 

 external condyle of the humerus ; and also to the capsular liga- 

 ment : inferiorly, to the autcro-superior part of the os mctacarpi 

 magnum. 



