564 THE ARTERIES. 



collateral and terminal divisions. It gives off a fine branch which accom- 

 panies the spur vein, and ramifies in the panniculus carnosus. 



This artery sometimes rises from the suprasternal vessel ; its volume 

 is subject to great variations, and we have seen it entirely absent. 



6. Inferior Cervical, or Trachelo-muscular Artery. (Fig. 282, 8, 8'.) 



Originating opposite the two preceding vessels, sometimes near the 

 external, and at other times near the internal mammary arteries, this vessel 

 is at first situated in the gulf between the jugulars, within the sterno-pre- 

 scapular muscle, and above the glands at the entrance to the chest ; it divides 

 after a short course into two branches, which separate at a very acute angle. 

 One of these, the superior (ascending cervical of Man), rises between the 

 mastoido-humeralis and subscapulo-hyoideus muscles, to which it is dis- 

 tributed, as well as to the glands at the point of the shoulder, and the sterno- 

 prescapularis and triangularis scapulae muscles. 



The inferior branch (thoracica acromialis of Man) descends in the in- 

 terstice comprised between the mastoido-humeralis and the sterno-humeralis 

 (pectoralis parvus) muscles, accompanying the cephalic vein; it is distri- 

 buted to these two muscles, the sterno-aponeuroticus (pectoralis transversus), 

 and the sterno-prescapularis. 



7. Superscapular, or Superior Scapular Artery. (Fig. 282. 13.) 



A small and slightly tortuous vessel, which arises from the axillary 

 artery, a little before it reaches the tendon of the subscapularis muscle. 

 It is directed upwards, and enters the space included between that muscle 

 and the super- (antea-) spinatus, after sending off some divisions to the sterno- 

 prescapularis muscle. Its terminal branches are expanded in the inferior 

 extremity of the super- and subspinati muscles, the tendon of the coraco- 

 radialis, and in the articulation of the shoulder. 



8. Inferior, or Subscapular Artery. (Fig. 347.) 



This artery is remarkable for its considerable volume; it arises at a 

 right angle from the axillary artery, at the space separating the subscapularis . 

 from the adductor of the arm. Its origin indicates the limit artificially 

 fixed between the brachial trunk and the humeral artery. It is seen to 

 proceed upwards and backwards in this interstice, within the large extensor 

 of the fore-arm, until near the dorsal angle of the scapula, where it 

 terminates. 



It gives off on its track : 



1. An artery which, following the inferior border of the great dorsal 

 muscle, ascends to its inner face, throwing off twigs into the substance of 

 the muscle as well as into the panniculus carnosus. 



2. The scapulo-humeral, or posterior circumflex artery of the shoulder, which 

 passes from within that articulation, beneath the great extensor muscle of 

 the shoulder, to reach its external face ; after giving off some collateral 

 branches, it arrives, with the circumflex nerves, underneath the abductors of 

 the arm, where it breaks up, like its satellite nerve, into several divergent 

 branches destined to the three muscles above named, the oblique flexor and 

 short extensor of the fore-arm, and to the mastoido-humeralis and panniculus 

 carnosus. 



