446 PRACTICAL ANATOMY. 



hypoglossal, and spinal accessory nerves ; the thoracic duct 

 on the left side, and on the right side the right lymphatic 

 duct. The common carotid artery on the right side is a 

 branch of the innominate ; on the left side it comes from 

 the arch of the aorta. It passes obliquely up the neck 

 in a line from the sterno-clavicular articulation to the 

 angle of the jaw, and at the upper border of the thyroid 

 cartilage it divides into the external and internal carotids. 

 The external carotid in the neck sends off the superior 

 thyroid, lingual, and facial to the structures anterior to 

 the vessel ; passing backward are the occipital and pos- 

 terior auricular. The ascending pharyngeal is deeply 

 placed behind the external carotid; it is given off just 

 above the bifurcation. External to the carotid artery is 

 the internal jugular vein, a capacious but delicate venous 

 trunk. It begins at the jugular foramen, at the base of 

 the skull, and receives the blood from the sinuses and 

 superficial and deep parts of the head and neck. It lies 

 in the same sheath with the carotid artery, from which it 

 is separated by a cellular interval. The descendens noni 

 from the hypoglossal forms a loop upon the sheath with 

 the communicans noni, derived from the second or third 

 cervical. 



The subclavian artery is divided into three portions by 

 the scalenus anticus muscle, from the first part, between 

 the muscle and the origin of the vessel, -are given off 

 the thyroid axis, the vertebral, and internal mammary; 

 from the second part, behind the scalenus anticus, comes 

 off the superior intercostal ; the third portion gives off no 

 branches. The subclavian artery arises about an inch 

 above the clavicle ; it rests on the cervical pleura, scale- 

 nus medius muscle, and the first rib. The subclavian vein 

 is in front of the artery, but on a lower level ; it receives 

 the external jugular and the transverse cervical veins. 



