THE CAT 231 



The Anterior Arteries. Study the right subclavian artery and 

 its main branches. The first of these to leave the subclavian is the 

 vertebral artery. This artery branches off from the dorsal side of 

 the subclavian at the first rib, passes forward, and enters the verte- 

 brarterial canal, in which it goes to the head. It enters the foramen 

 magnum and, joining the left vertebral artery, forms the median 

 basilar artery of the brain. 



The internal mammary artery leaves the ventral side of the sub- 

 clavian near the vertebral artery and passes back, along the inner 

 surface of the sternum, to the abdominal cavity, where it finally 

 anastomoses with the epigastric artery. 



The costocervical artery arises from the subclavian just back of 

 the vertebral artery ; it divides at once into two branches, which 

 supply the intercostal muscles and the muscles of the back 

 and sides. 



The thyrocervical axis arises opposite the internal mammary 

 artery and passes forward to the muscles of the shoulder and neck 

 and to the thyroid gland. 



The continuation of the subclavian is called the axillary artery. 

 It lies immediately behind the brachial plexus, which is a net- 

 work of large nerves in the axillary region. It gives off two small 

 arteries and then divides into the subscapular and the brachial. 

 The former passes toward the shoulder, where it gives off branches 

 which supply the muscles of the shoulder. The brachial artery 

 goes to the arm, which it supplies with blood. Follow these arteries 

 and their branches. 



Exercise 20. Draw a diagram showing the distribution of the sub- 

 clavian artery and its branches so far as observed. 



Study the right carotid artery and its branches, which pass 

 forward alongside the trachea to the head. Just in front of the 

 thyroid gland it gives off the thyroid artery. The muscularis 

 artery branches off very near the thyroid and goes to the muscles 

 of the neck. At the base of the neck the large lingual artery goes 

 to the under side of the face and to the tongue, and the external 

 maxillary to the side of the face. At the base of the ear the 

 posterior auricular artery passes to the muscles of the ear and the 



