THE VESSELS. 313 



(in common with it and cervical, superfic., when the last arises internal to 

 mm. scaleni). Course : obliquely outwards and downwards under cervical, 

 superficial., behind the clavicle, above the superior border of the scapula 

 (over lig. incisuras semilunaris) to the fossa supra- and infra- spinata. Situa- 

 tion: at first covered by sterno-cleidom., then by subclavius, before scalen. 

 anticus, art. subclavia, andplex. brachialis, above ven. subclavia, afterwards 

 under trapezius ; on the scapula between the bone and supraspinatus. 

 Branches to subclavius, trapezius, supra- and infra- spinatus, and periosteum 

 of acromion. 



5. Cervicalis profunda. Or. : the furthest outwards, in common with art. 

 intercostal, prima. Course : upwards and backwards, then outwards between 

 proc. transvers. of the seventh vertebra and the first rib, upwards upon multi- 

 fidus and semispin. cervicis as far as the atlas ; a branch descends to the mid- 

 dle of the back between longissimi dorsi. Situation : behind scaleni, then 

 deeper. Branches : to the deep layers of cervical muscles. 



558. Inferior branches of the Subclavia. 



6. Intercostalis prima, supplies the first and second (and third) intercostal 

 space. Or. : behind, under A. cervical, profunda. Course : passes before the 

 neck of the first rib, curving backwards and downwards on the outside of 

 gangl. dorsale, to the inferior border of the first (and second) ribs. Branches : 



a. Ramus dorsalis ; passes backwards, sends a ramus spinal, through 

 foram. intervertebr. 



b. Ram. intercostalis passes forwards between mm. intercostales. 



7. Mammaria (s. thoracicd) interna, the internal mammary artery. Or. : in 

 front under Art. thyreoid. inferior. Course : vertically downwards behind the 

 sternal extremity of the clavicula and the cartilages of the first to the sixth 

 ribs, where it divides into an external and an internal branch. Situation : at 

 first behind m. scalenus antic, and n.phrenicus, then upon the inner side of the 

 last, a line and a half to two lines from the border of the sternum, before m. 

 triangular, sterni and pleura. 



Branches. 1. Posterior, in the chest. 



a. Artt. thymicce, in children very large, to the Thymus. 



b. Art. phrenica superior, with N. phrenicus, passes between pericardium 

 and anterior mediastinum to the diaphragm. Branches to the pericardium, 

 Thymus. 



2. External branches of the mammaria interna. 



c. Artt. intercostales anteriores ; the two pass to the superior and inferior 

 borders of the first and second intercostal spaces ; supply mm. intercost. 

 and pleura, anastomosing with artt. intercostales posterr. (see Aorta). 



3. Anterior branches of mammaria interna. 



d. Artt. mammaria; externcs (six to seven) pass directly from behind for- 



