782 THE VASCULAR SYSTEM. 
internal and external intercostal muscles. The branches terminate by anastomosing with 
anterior intercostal branches of the internal mammary artery. Each gives off muscular 
branches to the intercostal muscles, a nutrient branch to the rib below which it lies, and a 
collateral branch which runs along the lower border of the space and terminates by 
anastomosing with an anterior intercostal branch of the internal mammary artery. 
THE AXILLARY ARTERY. 
The axillary artery (a. axillaris) hes in the axillary space. It is the direct 
continuation of the subclavian artery, and it becomes the brachial artery. 
The axillary artery commences at the outer border of the first rib, at the apex 
of the axillary space. It descends, with an outward inclination, along the external 
VE Subclavius . 
ee e Brachial plexus 
Deltoid Axillary 
artery 
Cephalic vein Acromio- 
~ thoracic artery 
Pectoralis minon _ Axillary vein 2 
AA: Ulnar nerve a 
; 
Posterior 
circumflex ees Long thoracic 
artery artery 
Coraco- 
brachialis = Long subseapular — 
Pectoralis | Se nerve 
major 
Subscapular 
Median <i] artery 
nerve : 
Dorsalis scapulir 
artery 
Teres major 
Latissimus dorsi 
Fic. 561.—THE AXILLARY ARTERY AND ITS BRANCHES AND RELATIONS. 
wall of the space, 7.e. to the inner side of the shoulder-joimt and the humerus, to the 
lower border of the teres major, where it becomes the brachial artery. A line 
drawn from the middle of the clavicle to the inner border of the prominence of the 
coraco-brachialis and biceps muscles, when the arm is abducted until it is at right 
angles with the side, indicates the position and direction of the artery. 
The position and direction, however, and to a certain extent the relations also 
of the axillary artery, are modified by changes in the position of the upper 
extremity. With the arm hanging by the side the axillary artery describes a 
curve with the coneayv ity direc ‘ted downwards and inwards, and the vein is to its 
inner side. When the arm is at right angles with the side, the axillary artery is 
almost straight, it les closer to the outer wall of the axilla, and the vein overlaps 
it in front and on the inner side. When the arm is raised above the level of the 
it arm te 
‘ 
i 
j 
® 
r 
