MUSCLES OF THE TRUNK. 233 



with the skin, which adheres intimately to it by means of a dense cellular 

 tissue, and with the sterno-humeralis, which covers its anterior border. 

 By its deep face, with the two portions of the deep pectoral, the coraco- 

 radialis (flexor brachii), and the long extensor of the fore-arm; it 

 also responds, by this face, to the antibrachial aponeurosis and the sub- 

 cutaneous vein of the fore-arm, which it maintains applied against that 

 aponeurosis. 



Action. It is an adductor of the anterior limb, and a tensor of the 

 antibrachial aponeurosis. 



2. Deep Pectoral (Figs. 114, 11, 13; 115, 1.) 



Synonym. The pectoralis parvus of Man. 



Volume Situation Composition. An enormous muscle, situated be- 

 neath the thorax, and composed, like the preceding, of two perfectly distinct 

 portions, described by Girard as two muscles, and designated by him as the 

 sterno-trochineus and sferno-prescapularis. 



A. STERNO-TROCHINEUS. Pectoralis magnus of (Percivall, Rigot, and) 

 Bourgelat. (The great sterno-humeralis of Leyh.) 



Volume Extent. This muscle, the largest of the two, offers a con- 

 siderajble volume. Extending from the ninth or tenth rib to the up|>er 

 extremity of the arm, it at first lies beneath and against the abdomen, then 

 beneath the chest, and at last is comprised between the walls of the latter 

 cavity, and the internal face of the anterior limb. 



Form. It is thin and flat above and below in its posterior third, thicker 

 and depressed from side to side in its middle third, and narrow and pris- 

 matic in its anterior third. Its general form may be compared to that of a 

 somewhat irregular triangle, elongated from before to behind, which would 

 have a very short posterior border, a longer internal or inferior border, and 

 an external or superior still more extensive. 



Structure. It is entirely composed of thick, parallel, fleshy fasciculi, all 

 of which leave the posterior or internal border of the muscle to gain its 

 narrow or anterior extremity. These fasciculi, as they approach the superior 

 border, become longer, and those which proceed from the posterior border com- 

 mence by aponeurotic fibres. Unfrequent intersections of fibrous tissue 

 exist towards the anterior extremity of the muscle. 



Attachments. It originates : 1, From the tunica abdominalis by the apo- 

 neurotic fasciculi of its posterior border ; 2, By its internal border, from the 

 posterior two-thirds of the inferior border of the sternum. It terminates, by 

 its anterior extremity, on the internal tubercle at the head of the humerus, 

 the tendon of origin of the coraco-humeralis, and the fascia enveloping the 

 coraco-radialis. Through the medium of this fascia, it is inserted into the 

 external lip of the bicipital groove formed by the great trochanter, and is 

 united to the two terminal branches of the supraspinatus muscles. (See 

 Fig. 114,12.) 



Relations. Its deep face, which is successively superior and internal, 

 covers the external oblique and the straight muscle of the abdomen, the 

 serratus magnus, costo-sternalis, and sterno-prescapularis, as well as some 

 thoraco-muscular nerves ; all these relations are maintained by means of a 

 loose and abundant cellular tissue. Its superior face, which alternately 

 looks downwards and outwards, responds : to the skin, from which it is 

 separated by a slight cellule-fibrous fascia ; to the sterno-aponeurofcicus ; 

 and to the muscles, vessels, and nerves of the inner aspect of the arm, through 



