768 



HUMAN ANATOMY. 



the two condyles of the humerus. When, however, the arm hangs vertically, the 

 vessel is slightly curved, the convexity of the curve looking upward and outward. 



Relations. — For convenience in description it is customary to regard the axil- 

 lary artery as consisting of three portions, the first of which is above the upper 

 border of the pectoralis minor, the second behind that muscle, and the third below 

 its lower border. 



The first portion of the artery is covered anteriorly by the clavicular portion 

 of the pectoralis major, by the costo-coracoid membrane which separates it from the 

 cephalic vein and the branches of the acromio-thoracic artery, and by the subclavius 

 muscle. The artery is enclosed along with its accompanying vein and the cords of 



Fig. 705. 



Pectoralis major, cut and everted 

 Deltoid 



Biceps, long head 



Superficial cervical 

 Posterior 

 Deltoid V scapular Trapezius 



Brachial plexus 



Transverse cervical 

 Subclavian artery 

 Scalenus anticus 

 Suprascapular 



\'ertebral 



.Inferior thyroid 

 Thyroid axis 



Subclavius mui 

 Acromial 

 thoracic 

 Superior 

 thoracic 



Alar thoracic 



Anterior circiunflex 



Axillary artery, third portion 



Biceps, short head 



Coraco-brachialis 

 Posterior circumflex ' 



. Dorsal scapular 

 Subscapular 



Serratus magnus- 



Subclavian and axillary arteries, pectoralis minor still in place. 



the brachial plexus in a downward prolongation of the cer\'ical fascia known as the 

 axillary sheath, and rests behind upon the .upper serration of the serratus magnus and 

 upon the first intercostal space. The internal anterior thoracic and the posterior 

 thoracic nerves cross it obliquely behind, the latter nerve intervening between it 

 and the serratus magnus. Above, at the outer side, are the cords of the brachial 

 plexus and the external anterior thoracic nerve, and below and to the inner side is 

 the axillary vein, between which and the artery is the internal anterior thoracic nerve. 

 In its second portion the artery is covered anteriorly by both the pectoralis 

 major and the pectoralis minor. Posteriorly it lies in contact with the posterior cord 

 of the brachial plexus, and is separated by a quantity of areolar and fatty tissue from 



