VEINS OF THE UPPER EXTREMITY. 375 



with each other, with the external, and with the internal jugular 

 vein. 



The Internal jugular vein, formed by the convergence of the lateral 

 and inferior petrosal sinus, commences at the foramen lacerum poste- 

 rius on each side of the base of the skull, and descends the side of the 

 neck, lying, in the first instance, to the outer side of the internal 

 carotid, and then upon the outer side of the common carotid artery to 

 the root of the neck, where it unites with the subclavian, and consti- 

 tutes the vena innominata. At its commencement, the internal jugu- 

 lar vein is posterior and external to the internal carotid artery, and 

 the eighth and ninth pairs of nerves ; lower down, the vein and artery 

 are on the same plane, the glosso-pharyngeal and hypoglossal nerves 

 passing forwards between them, the pneumogastric being between and 

 behind in the same sheath, and the nervus accessorius crossing ob- 

 liquely behind the vein. 



The Branches which the internal jugular receives in its course are, 

 the facial., the lingual, the inferior pharyngeal, the occipital, and the 

 superior and inferior thyroid veins. 



The Vertebral vein descends by the side of the vertebral artery 

 in the canal formed by the foramina in the transverse processes of the 

 cervical vertebrae, and terminates at the root of the neck in the com- 

 mencement of the vena innominata. In the lower part of the vertebral 

 canal it frequently divides into two branches, one of which advances 

 forwards, while the other passes through the foramen in the transverse 

 process of the seventh cervical vertebra, before opening into the vena 

 innominata. 



The Branches which it receives in its course are the posterior condy- 

 loid vein, muscular branches, the cervical meningo-rachidian veins, and, 

 near its termination, the superficial and deep cervical veins. 



The Inferior thyroid veins, two, and frequently more in number, are 

 situated one on each side of the trachea, and receive the venous blood 

 from the thyroid gland. They communicate with each other and 

 with the superior thyroid veins, and form a plexus upon the front of 

 the trachea. The right vein terminates in the right vena innominata, 

 just at its union with the superior cava, and the left in the left vena 

 innominata. 



VEINS OP THE UPPER EXTREMITY. 



The veins of the upper extremity are the deep and superficial. 

 The deep veins accompany the branches and trunks of the arteries, and 

 constitute their venae comites. The vena? comites of the radial and 

 ulnar arteries are enclosed in the same sheath with those vessels, and 

 terminate at the bend of the elbow in the brachial veins. The 

 brachial venae comites are situated one on each side of the artery, and 

 open into the axillary vein ; the axillary becomes the subclavian, and 

 the subclavian unites with the internal jugular to form the vena inno- 

 minata. 



