THE TORE EXTREMITY. 203 



and becomes inserted into the upper part of tlie ridge 

 running down from the external tubercle. The inner sur- 

 face of the first head is attached to the capsular ligament 

 of the shoulder- joint. 



Teres externus arises from faschia which covers postea 

 spinatus and extends as far forwards as the spine of the 

 scapula, also from the superior part of the posterior costa 

 of the scapula. It is at first composed of two layers, but 

 these combine inferiorly to become inserted into the lower 

 part of the humeral ridge. Between this tendon and the 

 lower tendon of postea spinatus the 



Scapulo-humeralis externus is inserted, after passing 

 over the capsular ligament of the shoulder-joint and becom- 

 ing attached to it, and arising from a roughened ridge at 

 the postero-external part of the neck of the scapula at the 

 lower part of the fossa postea spinatus in front of caput 

 magnum, extending to a slight extent around its inferior 

 extremity to its posterior surface. By removing the superior 

 attachment of this muscle, we generally expose a branch 

 from the posterior scapular artery passing through the 

 medullary foramen of the scapula. 



Underneath the above-named muscles to the posterior 

 surface of the humeral ridge the 



Caput medium of the triceps extensor brachii is attached. 

 The triceps is that large mass of muscle which fills up the 

 triangular space between the scapula and the humerus ; 

 as its name indicates, it consists of three parts or heads, 

 named according to their respective sizes. Caput magnum 

 is attached superiorly along the major portion of the pos- 

 terior costa of the scapula, not extending, however, to 

 the extreme inferior part. It is attached to the cap- 

 sular ligament of the shoulder- joint and covers scapulo- 

 humeralis posticus, and at the extreme inferior part becomes 

 large and thick, and internally to its superior attachment 

 presents a groove in which rests the teres major vel in- 

 ternus ; between the two muscles is the posterior scapular 

 artery with its accompanying vein and nerve. It is a branch 

 of the axillary artery and runs upwards, sending branches 

 to the muscles, between which it runs to subscapularis. 

 The fibres of this head converge, and run towards the point 

 of the ulna, into which they become inserted through the 

 medium of a short stout tendon which passes over a bursa 

 prior to insertion. Caput medium runs from the posterior 



