450 



DISSECTION OF THE THORAX. 



and upper 

 cava. 



carotid, and left subclavian. On its left side of the aorta, and 

 within the concavity of its arch, is the pulmonary artery. 



theninno- Ahove the arch of the aorta a large venous trunk, left 



mmate vcms innominate, crosses over the three arteries mentioned ahove, and 



ends by uniting on the right side with the right innominate vein 



in the upper cava. Several small veins, which may be mistaken 



for nerves, ascend over the aorta, and enter the left innominate. 



and Define the tributaries of this vein, and especially one crossing 



' ies ' the aortic arch towards the left side, which is the left superior 



intercostal vein. The inferior thyroid vein, which descends in 



front of the trachea to open into the left innominate vein or into 



the junction of the two innominate A T eins, should also be dissected 



out. 



The large vein by the side of the aorta is the superior vena cava ; 

 and the azygos major vein will be found opening into it behind, above 

 the aorta of the right lung. 



The phrenic nerves should be cleared on both sides from their 

 entry into the thorax behind the subclavian veins above, along the 

 side of the pericardium to the diaphragm below, as well as the left 

 vagus nerve, which lies deeply upon the aortic arch, and will be 

 found coming downwards in front of that vessel from between the 

 origin of the left common carotid and subclavian arteries. Between 

 the left phrenic and vagus nerves and close to the aorta are the left 

 superficial cardie nerve of the sympathetic, and the lower cervical 

 cardiac branch of the left vagus ; of the two, the last is the smaller, 

 and in front of the other. 



The cardiac nerves from the left vagus and sympathetic are to be 

 followed to a small plexus (superficial cardiac) in the concavity of 

 the aorta. An offset of the plexus is to be traced downwards 

 between the pulnicnary artery and the aorta towards the right 

 coronary artery of the heart ; and another prolongation is to be 

 found coming forwards from the deep cardiac to the superficial 

 plexus ; this dissection is difficult, and requires care. 



When the pericardium is afterwards opened the nerves will l>t> 

 followed on the heart. 



The PERICARDIUM is somewhat conical in form, the wider part 

 being turned towards the diaphragm, and the narrower part 

 extending upwards beyond the heart on the large vessels. It is 

 placed behind the sternum, and projects on each side of that bone, 

 but much more towards the left than the right side. Laterally the 

 pericardium is covered by the pleura, and the phrenic nerve and 

 vessels lie between the two. Its anterior surface is separated from 

 the chest-wall by the pleursB and lungs, except over the small area 

 on the left side corresponding to the lower part of the anterior 

 mediastinum ; and behind, in the interval between the pleurae, it 

 is in contact with the oesophagus and aorta. 



The heart-case consists of a fibrous structure, which is lined 

 internally by a serous membrane. 

 Fibrous part The fibrous part surrounds the heart, and is pierced by the large 

 sheaths to vessels joining that organ ; and, with the exception of the inferior 



vessels. 



Nerves. 



Dissect 

 superficial 

 plexus in 

 arch of 

 aorta. 



Pericar- 

 dium : 

 size and 

 form ; 



position 



relations. 



Composi- 

 tion. 



