386" DR. C. F. SONNTAG ON THE ANATOMY, 



Arteries of the Pectoral Extremity. 



Subclavian Arteries (text-fig. 38. R.S.A. and L.S.A) : — The 

 branches of the extra-thoracic parts differ from those in Man, 

 but the parent vessels are similar, though relatively larger. The 

 branches are : — 



1. Vertebral Artery (Y.A) which is very large. It enters the 

 foramen in the sixth cervical vertebra along with sympathetic 

 nerves from the inferior cervical ganglion of the sympathetic. 



2. A large ti-unk whose branches correspond to separate 

 branches of the human subclavian. Its first set of branches, 

 which arise together, are : — 



a. Spinal Arteries (S.A) entei-ing the lower fovir intervertebral 

 foramina behind the corresponding nerves. 



b. Profunda cervicis (P.O. A) which passes between the trans- 

 verse process of the seventh cervical vertebra and the neck of the 

 first rib. It ascends among the muscles of the back of the neck, 

 supplies them, and anastomoses with the occipital artery. 



c. Muscular branches to the prevertebral muscles. 



The trunk then runs outwards, gives ofi' an ascending branch 

 (A.B) to the muscles in the floor of the posterior triangle and 

 the upper four spinal foramina and the long thoracic artery 

 (L.T.A). Finally it divides into the suprascapular artery (S-S.A), 

 and a branch corresponding to the descending branch of the trans- 

 verse cervical artery in Man (D.T.A). These terminal branches 

 course much as in Man. 



No inferior thyroid artery is present, its place being taken by 

 a branch of the common carotid artery. 



3. Prevertebral muscular artery. 



4. Superior intercostal artery (S.I. A) is large. It runs over 

 the neck of the first rib, gives very small branches to the first 

 two interspaces, and is continued as a very large artery into the 

 first thoracic intervertebral foramen. 



5. The internal mammary artery (I.M.A.) arises close to the 

 inner border of the scalenus anticus along with the superior 

 intercostal artery, and its relations are as in Man. It divides at 

 the fifth interspace into superior epigastric and musculo-phrenic. 

 It gives ofiT an artery which breaks up into branches to the 

 thymus, pericardium, and mediastinum, and anastomoses with 

 the thyroidea ima. Muscular branches run to the triangularis 

 sterni. But the intercostal arteries are not as regularly disposed 

 as in Man. The phrenic artery divides into two at the seventh 

 chondro-costal junction ; one branch turns inwards and enters 

 the diaphragmatic musculature, and the other continues along 

 the origin of the diaphragm to the mid-axillary line where it 

 enters the diaphragm. It anastomoses with phrenic branches 

 of the lower intercostal arteries. 



Branches of the suprascapular and descending branch of the 

 transverse cervical arteries take the place of the superior thoracic 



