480 



DISSECTION OF THE THORAX. 



aud veins. 



Bronchial 

 arteries, 



and veins. 



Lympha- 

 tics, 



Pulmonary 

 nerves. 



The pulmonary veins are not so regular in their arrangement as 

 the arteries. They arise from the network of the air-cells ; and the 

 branches from adjoining lobules communicate freely together. The 

 larger branches for the most part lie in front of the airtubes which 

 they accompany. The pulmonary veins have no valves. 



The bronchial arteries are derived directly or indirectly from the 

 aorta, two for the left lung and one for the right (p. 481), and 

 enter the lung on the airtube, which they also follow in its ramifi- 

 cations. They distribute branches to the bronchial lymphatic 

 glands, to the walls of the larger blood-vessels and bronchial tubes, 

 and to the interlobular connective tissue. Other small offsets ramify 

 on the surface of the lung beneath the pleura. On the smallest 

 bronchial tubes minute branches anastomose with offsets of the 

 pulmonary arteries. 



The bronchial veins begin by twigs corresponding with the super- 

 ficial and deep branches of the artery, and leave the root of the 

 lung to end in the azygos veins. Many of these veins, however, open 

 into the pulmonary veins, both within the lung and in the root. 



The lymphatics of the lung are superficial and deep ; the latter 

 accompany both the bronchia and the branches of the pulmonary 

 vessels. All pass to the bronchial glands at the root of the lung. 



The nerves of the lung are derived through the pulmonary 

 plexuses from the vagus and sympathetic, and follow the branches 

 of the airtube. They have minute ganglia connected with their 

 filaments. 



PARTS OF THE SPINE AND THE SYMPATHETIC CORD. 



Dissection 

 of thoracic 

 duct, 



of other 

 objects, 



and of sym- 

 pathetic. 



Descending 

 thoracic 

 aorta ; 



In front of the spinal column are the objects in the interpleural 

 space of the posterior mediastinum, viz., the aorta, azygos veins, 

 thoracic duct, and oesophagus ; and beneath the pleura on each side 

 of the spine is the sympathetic nerve. 



Dissection (fig. 174). The thoracic duct should be found first 

 near the diaphragm by removing the pleura ; there it is about as 

 large as a crow-quill, and rests against the right side of the aorta. 



The areolar tissue and the pleura are to be cleared away from the 

 different structures before mentioned ; and the azygos veins, one 

 on the right and two on the left of the aorta, should be dissected. 

 Next follow the thoracic duct upwards beneath the arch of the 

 aorta, and along the oesophagus beneath the pleura, till it leaves 

 the upper aperture of the thorax. 



After raising the pleura from the inner surface of the vertebrae 

 and ribs, the gangliated cord of the sympathetic nerve will be seen 

 lying over the heads of the ribs. Branches are to be followed out- 

 wards from the ganglia to the intercostal nerves ; and others inwards 

 over the bodies of the vertebrae, the lowest and largest of these 

 forming the three trunks of the splanchnic nerves. 



The DESCENDING THORACIC AORTA is the part of the great systemic 

 vessel between the termination of the arch and the diaphragm. Its 



