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RESPIRATORY APPARATUS IN MAMMALIA. 



The external or costal face is convex (and smooth), and moulded to the 

 external wall, of the thorax. 



The internal, or mediastinal face, forms a vertical plane, separated from the 

 opposite lung by the mediastinum. It shows : 1. A small anterior portion in 

 contact with the anterior mediastinum. 2. At the heart, an excavation in which 

 that organ is lodged. 3. Immediately behind this excavation, and a little above 

 it, the root of the lung (hilum-pulmonis) — a fasciculus formed by the air-tubes and 

 pulmonary vessels in entering the viscus. 4. A posterior portion, more extensive 

 than the other two put together corresponding to the posterior mediastinum, 



LUNG OF THE HORSE, SUSPENDED BY THE TRACHEA (VIEWED BY ITS BASE AND INFERIOR BORDER). 



T, Trachea; L, L', anterior lobes; E, E', cavity for the heart ; Ap, Ap, branches of the pulmonary 

 artery at their entrance to the heart; Vp, Vp, pulmonary veins at their emergence from the 

 lung ; F, F, external face of the lobes of the lung ; D, D, b.ase of the lung, or diaphragmatic face 

 of the two lobes; H, internal lobule of the right lobe ; I, channel for the posterior vena cava; 

 0, oesophagus passing between the two lobes (a certain retraction of the organ appears to make 

 it pass between the lobe and lobule of the right lung). 



and attached to that septum by means of a fold developed around the organ, to 

 form the pulmonary pleura ; this fold constitutes, posteriorly, a small serous 

 ligament {ligamentum latum pulmonis), attached at once to the mediastinum and 

 the posterior face of the diaphragm. On this portion of the lung are remarked 

 two antero-posterior furrows : one, near the upper border of the organ, to 

 receive the thoracic aorta ; the other situated lower, but not so deep, more 

 marked in the left than the right, and lodging the oesophagus. In the right 



