THE BRACHIAL OR AXILLARY ARTERIES. 561 



times long and voluminous, and partly supplements the superior cervical, 

 as is exemplified in the specimen which served for Fig. 282. 



Before leaving the thorax, the dorsal artery gives off some unimportant 

 ramuscules and the subcostal artery (superior intercostal of Man). This 

 branch (Fig. 282, 5) curves backwards and, with the sympathetic chain, places 

 itself beneath the costo-vertebral articulations, against the long muscle of 

 the neck, furnishing the second, third and fourth intercostal arteries and 

 the corresponding spinal branches, and terminating at the fifth intercostal 

 space by either forming the artery which descends into that space, in 

 anastomosing by inosculation with a branch emanating from the first 

 posterior intercostal artery, or by expending itself in the spinal musclep. 

 Frequently the second intercostal and its spinal branch come directly from 

 the dorsal artery ; the fifth also often arises from the posterior aorta. 1 



On the right side, the dorsal artery always proceeds from a trunk common 

 to it and the superior cervical artery : a circumstance sometimes observed in 

 the left. This trunk has no relation with the oesophagus. 



2. Superior Cervical, Cervico-muscular, or Deep Cervical Artery. 

 (Fig. 282, 6.) 



This vessel arises in front of the preceding artery, affects the same 

 relations in the thoracic cavity, which it leaves by passing between 

 the two first ribs, behind the last costo-transverse articulation; 2 it is 

 then directed upwards and forwards, passing beneath the inferior branch of 

 the ilio-spinal and great complexus muscles, courses in a flexuous manner 

 through the space comprised between the latter muscle on one side, and 

 the superior branch of the ilio-spinalis and cervical ligament on the 

 other, and arrives at the second vertebra of the neck, where its terminal 

 divisions anastomose with the branches of the occipito-muscular, vertebral, 

 and even the dorsal, arteries. 



The superior cervical artery distributes in its course : 1, The first inter- 

 costal artery and the first spinal branch ; 2, Very numerous branches which 

 are expended in the muscles and integuments of the cervical region, as well 

 as in the large ligament occupying the middle plane of that region ; among 

 these branches, one longer than the others traverses the great complexus 

 muscle to place itself between it and the splenius, and which is sometimes 

 supplemented in great part by the dorsal artery. 



3. Vertebral Artery. (Fig. 282, 7.) 



Arising at an acute angle from the axillary artery at the first intercostal 

 space, and covered at its origin by the mediastinal layer, the vertebral 

 artery proceeds forward and upward, within the first rib, outside the 

 oesophagus, 3 the trachea, and the inferior cervical ganglion, and is situated 

 at the bottom of the interstice separating the two portions of the scalenus, 

 with the fasciculus of branches originating from the brachial plexus, which 

 is a little above the vessel. It then passes beneath the transverse process 

 of the seventh cervical vertebra, and traverses the series of cervical 

 foramina, hidden beneath the intertransverse muscles, to anastomose in 



1 For the description of these arteries, see page 524. 



2 We have seen it escape, along with the dorsal artery, by the second intercostal 

 space. 



3 On the right, these relations with the oesophagus are not present. 



