RESPIRATORY ORGANS. 253 
left (’-8’). It divides into three smaller proximal lobes (1-8), 
and one large distal one (4). The most cranial one of the 
proximal lobes (1) is sometimes partly subdivided. The third 
one of the proximal lobes (3) lies mediad of the others; it is 
partly subdivided and one-half projects into a pocket in the 
Fic. 106.—RAMIFICATIONS OF THE BRONCHI, WITH OUTLINES OF THE LOBES 
OF THE LUNGS, VENTRAL VIEW. 
1-4, lobes of the right lung; 1’-3’, lobes of the left lung. a, trachea; 4, 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 (1-3'); the 
two cranial ones (1’-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 Jung is attached to the aorta, vertebral column, and 
diaphragm by a fold of pleura, the pulmonary ligament. This 
