MUSCLES OF THE ANTERIOR LIMBS. 251 



is prismatic, muscular, divided by fibrous intersections, and easily separated 

 into several irregular fasciculi. In its superior half it is flattened, entirely 

 tendinous, and split into several digitations, the longest of which are behind. 



Attachments. It originates 1, Through the medium of its tendinous 

 digitations, from the posterior border of the scapula and the linear imprints 

 in the posterior spinous fossa ; 2, From the small tubercle situated on the 

 external side of the margin of the glenoid cavity, by a short tendon. It 

 terminates on the humerus, between the crest of the external tubercle and 

 the deltoid imprint. 



Relations. Outwardly, with the subspinatus and the long abductor; 

 inwardly, with the large extensor of the fore-arm, the short extensor, and the 

 capsule of the scapulo-humeral articulation. 



Action. Like the preceding, this muscle is an abductor and outward 

 rotator of the humerus. 



4. Superspinatus. (Figs. 119, 2 ; 121, 5.) 



Synonyms. Superacroiuio-trodiiterius Girard. (Antea spinatus PercivaU. An- 

 terior spinatus Leyh.) 



Form Situation. This muscle is thick and prismatic, stronger below 

 than above, representing a very elongated pyramid, and completely filling, 

 and even projecting beyond, the super- scapular fossa. 



Structure Attachments. It is almost entirely formed of fleshy fibres, 

 which are attached, by their superior extremities, to the cartilage of prolong- 

 ment of the scapula, the inner face of the scapular aponeurosis, the super- 

 scapular fossa, and the anterior border and cervical angle of the scapula 

 fixed insertion. These fibres, on reaching the inferior extremity of the 

 muscle, form two very thick, short, and slightly tendinous branches, united 

 to each other by the enveloping coraco-radial or biceps aponeurosis. The 

 external branch reaches the summit of the external tubercle : the internal is 

 inserted into the corresponding part of the internal tuberosity movable 

 insertion. 



Relations. Outwards, with the scapular aponeurosis, to which its fibres 

 adhere in the most intimate manner inwards, with the scapula and the sub- 

 scapularis muscle ; forwards, with the small pectoral ; and behind, with the 

 acromion spine and the subspinatus. The two terminal branches cover and 

 embrace the coraco-radialis tendon, and the capsule of the scapulo-humeral 

 articulation. 



Action. This muscle is an extensor of the humerus, and a tensor of the 

 enveloping coraco-radial aponeurosis. With regard to the articulation of the 

 shoulder, it plays the part of a powerful ligament : a function it shares with 

 the majority of the other scapular muscles. 



5. Subspinatus. (Fig. 119, 3, 3'.) 



Synonyms. Sub-acromio-trochiterius Girard. (Posted spinatus Percivall. Pos- 

 terior spinatus Leyh.) 



Situation Form. Situated, as its name indicates, in the subspinatus 

 fossa, this muscle is wide, thin, and flattened on both sides at its superior 

 extremity, thick and prismatic in its middle, and conoid at its inferior 

 extremity, which is terminated by two short branches an external and 

 internal. 



