334 ANATOMY OF THE RABBIT 



(a) Each pleural cavity (cavum pleurae) is a closed serous sac, 

 the lining membrane, or pleura, being distributed over the 

 costal surface as the costal pleura, partly over the anterior 

 surface of the diaphragm as the diaphragmatic pleura, 

 and over the surface of the lung as the pulmonary pleura, 

 and entering into the formation of the mediastinum as the 

 mediastinal pleura. 



A secondary fold on the right side of the mediastinal septum con- 

 tains the inferior vena cava and forms a pocket in which lies the medial 

 lobule of the inferior lobe of the right lung. The attachment of the 

 posterior margin of the septum to the diaphragm is displaced to the 

 left so that it and the secondary fold are approximately symmetrical 

 and the pleural pocket is median. Posteriorly, the pulmonary pleura 

 passes from the medial margin of the left lung and from the medial 

 margins of both inferior lobules of the right lung to the mediastinal 

 septum and backward to the diaphragm, forming the pulmonary 

 ligament (lig. pulmonale). These relations may be understood more 

 clearly by reference to a transverse section such as that represented 

 diagrammatically in Fig. 113. 



{b) The lungs (pulmones) are paired expansible structures, the 



surfaces of which are free, except medially, where they are 



connected with the respiratory passages and the pulmonary 



blood-vessels, and posteromedially, where they are attached 



to the mediastinum and to the diaphragm by the pulmonary 



ligaments. 

 (c) The right lung is divided by deep fissures into superior, 



middle, and inferior lobes, the 



inferior lobe consisting of a 



large lateral lobule and a 



smaller medial lobule, the last 



frequently further subdivided. 



The inferior caval vein passes 



between these lobules. The 



left lung is only about two 



. . , r , , • r . 1 • v. Fig. 114. Plan of the respiratory 



thirds Ot the size OI the right tubes as seen from the ventral sur- 



1 J l.*-U^ U 4-U ,.^:^^1^ face, tr, trachea; br, br', left and 



lung and, although the middle ^ight bronchi; ep, eparterial bron- 



nr^A I'nf orir^r lrkhi:^c ^ r^ \\7f^]] ^^^^> ^' "^' "^'' ^' ^'' bronchial rami to 

 and interior lOOeS are wen superior, middle, and inferior lobes; 



developed, the superior lobe is iJ;^J-j /Xuief'^ '"""^ '° ^'''''^ ^"^ 



very imperfectly represented. 



The inferior lobe of the left lung is not subdivided. 



