DISSECTION OF THE BACK AND THORAX. 119 



cervical arteries, which have precisely the same course and distribution 

 as those of the left side. They have also the same connections, save that 

 they do not touch the oesophagus. 



The Cephalic Ahtery. This vessel, which has a length of about two 

 or three inches, passes directly forwards at the lower face of the trachea, 

 and bifurcates at the entrance to the chest, forming the common carotid 

 arteries (right and left). 



The Right Axillary Artery. This vessel in its intrathoracic course 

 forms a continuous curve, or arch, with the arteria innominata; this 

 arch being, however, on a lower level, and less abrupt, than that of the 

 left axillary. It gives oflp here the vertebral and internal thoracic arteries. 



The Vertebral Artery and the Internal Thoracic Artery do not 

 differ from the homonymous vessels of the left side. 



The Anterior Vena Cava. This large vessel, already referred to, is 

 best seen from the right side of the chest. It is formed at the entrance 

 to the chest by the union of the jugular and axillary veins of both sides, 

 and its initial portion is fixed by fibrous processes to the inner surfaces 

 of the first pair of ribs. It passes backwards through the anterior medias- 

 tinum, being there related to the great arteries, beneath and to the right 

 of which it is placed. * It enters the roof of the right auricle. Besides the 

 vessels already seen entering it on the left side (page 14), it receives — 



1. The Internal Thoracic Vein. 



2. The Vertebral Vein. 



3. A trunk formed by the union of the dorsal and superior cervical 

 veins. (These veins may enter independently.) 



4. The Great Vena Azygos (sometimes). This large vein begins 

 behind the hiatus aorticus, where it receives the first pair of lumbar 

 veins. Passing through the hiatus, it extends along the dorsal portion 

 of the spine to the right of the posterior aorta, the thoracic duct being 

 usually between the two vessels. At the 6th or 7th dorsal vertebra 

 it leaves the spine and curves downwards to the right of the aortic arch, 

 the oesophagus, and the trachea; terminating either in the anterior vena 

 cava, or in the auricle immediately behind the opening of that vein. 

 Besides the first pair of lumbar veins, it receives the last thirteen 

 intercostal veins of the right side and the last five or six of the left. 



The Posterior Vena Cava. This great vein enters the thorax 

 through the foramen dextrum of the diaphragm. It passes directly 

 forwards to terminate in the light auricle, being included between the 

 main mass of the right lung and its internal lobule, and placed at the 

 upper edge of a double serous fold belonging to the right pleural mem- 

 brane. The right phrenic nerve is in company with it. 



The Eight Lymphatic Duct. This is a short lymphatic vessel (not 



* The vein is in the natural position in Plate 25. In Plates 24 and 26 it is represented as smaller 

 than natural, and slightly lowered in position, in order to expose the arteries. 



