LUNGS 



297 



The cartilages of the bronchi become more and more sparse and 

 finally disappear as the latter divide up into finer and finer 

 branches. 



The thoracic cavity is lined by a serous membrane, the pleura, 

 in which, as in the case of the peritoneum (p. 235), a parietal and 



T* 



FIG. 240A. LUNG OF MAN. (From the ventral side. ) 



1, 2, 3, lobes of the right, and 2a, 3a, of the left lung ; Z, base of lung ; t, incisura 

 cordis ; S, sulcus for the subclavian artery ; Tr, trachea. 



FIG. 240s and c. DIAGRAM OF THE PLEURAL AND PERICARDIAL CAVITIES OF 

 MAMMALS, FOUNDED ON THE RELATIONS OF THESE PARTS IN MAN. (B, 



horizontal section ; C, transverse section. ) 



Tr, trachea ; Br, bronchi ; L, L, lungs ; H, heart ; W, vertebral column ; P, 

 parietal, and P 1 , visceral layer of the pleura ; ft, points at which these pass 

 into one another at the hilum pulmonalis (Hi) ; m, mediastinum ; PC, Ps l , 

 parietal and visceral layers of the pericardium ; If, ribs (wall of thorax) ; S, 

 sternum. 



visceral layer may be distinguished (Fig. 240, B, C) : the latter is 

 spoken of as the pulmonary pleura, the former as the costal pleura. 



