THE TRUNK. 453 



702. Axillary cavity, fovea axillaris, Axilla, 



is triangular ; its base directed towards the chest, its apex towards 

 the inner side of the upper arm, its anterior wall is formed by m. 

 pectoralis major, minor, and the anterior portion of the deltoideus ; 

 its posterior wall by m. latissimus dorsi, teres major, and subscapu- 

 laris ; the inner wall by m. serratus magnus and the chest ; the 

 external wall by m. biceps, coraco-brachial., upper arm (the upper- 

 most part). The blunt apex forms a triangular opening, which is 

 in connexion with the reg. supraclavwularis ; formed in front by 

 the clavicula, behind by the superior border of reg. scapularis, in- 

 ternally and below by the first rib. 



703. Fossa infraclavicularis, 



is the name given to a triangular excavation on the anterior wall 

 of the axilla, through which we pass to the apex of that fossa. It 

 is bounded externally by the head of the humerus ; internally, by 

 proc: coracoid. ; above, by clavicula and acromion ; and arises from 

 the fissure between m. deltoid, and pectoralis major. Before it 

 pass vena cephalica and art. acromialis. Behind that vasa and 

 nn. thoracici externi ; m. pectoralis minor and fasc. coraco-clavi- 

 cularis, m. subclavius. Beneath the hairy and thin skin at the base 

 of the axilla, which is largely supplied with sebaceous follicles, a 

 loose adipose areolar tissue is found, some superficial lymphatic 

 glands, fasc. brachialis (between m. pectoral, maj. and latissim. 

 dorsi), branches of vasa axillar. and the v. axillaris, deep lym- 

 phatic glands, vena and art. axillaris, the trunks of nerves, lami- 

 nated areolar tissue, and the shoulder joint. 



Art. axillaris passes : a. between the first rib and the superior 

 border of m. pectoral, minor, on the outer side of v. axillaris, on the 

 inner of the inferior branch of plex. nerv. brachialis and proc. cora- 

 cold., supported upon m. intercostal. 7.,the second rib, and m. serrat. 

 antic, major. ; b. behind pectoralis minor, covered by the two roots 

 of the n. medianus before, closer to the humerus ; c. from the infe- 

 rior external border of m. pectoral, minor, as far as to the inferior 

 limit of the axilla, behind v. axillar., internal to and behind nerv. 

 medianus, m. coraco-brachial., cap. breve bicip., and os humeri ; 

 before nerv. ulnaris, before and internal \on. radialisand axillaris. 

 Behind it, plex. lymphaticus, tendons of subscapularis, m. latissim. 

 dorsi. The direction of art. ven. axillaris, and the plex. brachialis, 

 is oblique from above and within, to below and without (from the 

 anterior internal angle of the axilla to its external). 



