THE LUNGS 



453 



The posterior mediastinum is very delicate below the oesophagus, and usually 

 appears fenestrated; when these apertures are present, the two pleural cavities 



communicate with each other/ • i uv. fV.or.0 i« 



The pleural sacs contain a serous fluid, the hquor pleurae; ni health there is 



only a sufficient amount to moisten the surface, but it accumulates rapidly after 



death. 



Costal pleura 



Pulmonary 

 pleura 



Pulmonary 

 artery 



Bronchus 



Area of adhe- 

 sion of lungs 



Left phrenic 

 nerve 



Mediastituil 

 pleura 



Mediastinal lobe 

 of right lung 



Vena azygos 



Thoracic duct 



A orta 



Superior oesopha- 

 geal 7ierve 

 (Esophagus 

 Inferior oesopha- 

 geal nerve 



Posterior vena cava 



Right phrenic 

 nerve 



Fold of pleura in- 

 closing posterior 

 vena cava and 

 rigid phrenic 

 nerve 



Stemiini 



Fig. 360 -Cross-section of Thorax of New-borx Foal. 

 Ribs are numbered. 



THE LUNGS 



The lungs (Pulmones) occupy much the greater part of the thoracic cavity. 

 They ar^ accurately adapted to Z walls of the cavity -^ the oth^^^^^^^^^^ 

 tained therein. The two lungs are not alike m form or size, ^^e nght one b^ng 

 considerably larger than the left; the difference is chiefly m width, m conformity 

 with the projection of the heart to the left. nrpssed 



The lung is soft, spongy, and highly elastic. It ^^P^t .t\Cadc 

 between the finger and thumb, and floats m water. When the thomc^ 

 cavity of the unpreserved subject is opened he lung ^^^^^Pf ^„ "^^"^^^^^f f, 

 to about one-third of its original size, and loses f «^ l^^P^^ • """ ' . ',^" " 

 due to its highly elastic character and the fact that the tension of the lung 



xThe apertures do not exist in the fa>tus, and are ^f ^-^^jJ^^^^^Vo" th^^ 

 side in the horse. 



