THE AXILLAKY AETEEY. 



915 



ioted that the upper border of the pectoralis minor is frequently exactly opposite 

 he external border of the first rib, at the point where the axillary artery begins, 

 n the strict sense, therefore; no part of the artery is above the pectoralis minor. 



Relations of the First Part Posterior. The first part of the artery is enclosed, 

 ogether with the vein and the cords of the brachial plexus, in a prolongation of the 

 ervical fascia known as the axillary sheath. Posterior to the sheath are the upper serra- 

 ion of the serratus anterior, the contents of the first intercostal space, and the long 

 horacic nerve, the latter descending vertically between the artery and the serratus 



A. transversa colli, ramus descenden 

 V. jugularis externa 



A. subclavia s % 

 A. transversa scapulae . 

 Xn. thoracales anteriores ' 



romialis et rami deltoideus et pectoralis ' X \ 

 A. et V., axillaris { \ X .' 

 M. deltoideus x \ \ 



A. carotis communis 

 V. jugularis interna | 



M. omohyoideus 



| M. sternothyreoideus 



M. pectoralis minor 



M. pectoralis major /~~ 

 M. latissimus dorsi 

 M. serratus anterior 

 M. obliquus externus abdomini 



FIG. 766. THE AXILLARY ARTERY AND ITS BRANCHES. 



, 



IE. --The middle third of the clavicle has been removed ; and the arm has been slightly abducted and 

 rotated laterally. Parts of the pectoralis major and minor have been removed ; the positipns of the 

 lower border of the pectoralis major and the upper and lower borders of the pectoralis minor are indi- 

 cated by broken black lines. Compare with Fig. 759, which represents a dissection of the same body 

 from a diiferent point of view. 



anterior ; whilst, within the sheath, the medial anterior thoracic nerve and the medial 

 cord of the brachial plexus lie behind the artery. Anterior. -It is covered in front by the 

 costo-coracoid membrane. The membrane intervenes between the artery and the cephalic 

 vein, the branches of the lateral anterior thoracic nerve, the branches of the thoraco- 

 acromial artery with their accompanying veins, and the clavicular part of the pectoralis 

 major muscle, superficial to which are the deep fascia, the platysma, the supra-clavicular 

 branches of the cervical plexus, and the superficial fascia and the skin. Posterior to the 

 costo-coracoid membrane the artery is crossed by a loop of communication between the 

 lateral and medial anterior thoracic nerves. Lateral. Above and to the lateral side are 



59 a 



