RESPIRATORY ORGANS. 



253 



left (i'-3'). It divides into three smaller proximal lobes (i-3), 

 and one large distal one (4). The most cranial one of the 

 proximal lobes (1 ) ^^ sometimes partly subdivided. The third 

 one of the proximal lobes (3) lies mcdiad of the others; it is 

 partly subdivided and one-half projects into a pocket in the 



Fig. io6. — Ramifications ok the Bronchi, with Outlines of the Lobes 



OF THE Lungs, Ventral View. 



1-4, lobes of the right lung; i'-t,', lobes of the left lung, a, trachea; b, epar- 

 terial bronchus. 



mediastinum, so that it comes to lie across the middle line, 

 extending a short distance onto the left side. This lobe is 

 frequently called the mediastinal lobe (3). The caudal lobe 

 (4) of the right lung is large and flat, containing about half the 

 substance of the lung. 



The left lung is divided into three main lobes ( i'-3' ) ; the 

 two cranial ones (i'-2') are, however, partly united at the base, 

 so that they may be considered subdivisions of but a single 

 lobe ; thus the left lung has but two distinctly separated lobes. 



Each lung is attached to the aorta, vertebral column, and 

 diaphragm by a fold of pleura, the pulmonary ligament. This 



