106 THE ANATOMY OF THE HORSE. 



and occupy but a small moiety of the cavity, a condition which makes 

 their examination more easy. Each lung appears to lie somewhat 

 loosely in the chest ; but if it be grasped, and an attempt be made to 

 remove it bodily, it will be found to be attached at a point on its inner 

 surface. This, which is termed the root of the lung, is the point where 

 the bronchi and vessels enter it. Each lung presents for examination 

 two surfaces, three borders, a base, and an apex. 



The External (or costal) hirface is much the larger of the two. It is 

 smooth and convex, and in health it is closely applied to the chest wall. 

 The internal (or mediastinal) surface is moulded on the mediastinum 

 and the organs contained in it. Thus, it presents opposite the heart 

 a depression for the lodgment of that organ; behind that point, and 

 near the upper limit of the surface, a longitudinal groove for the pos- 

 terior aorta; and beneath that again a second furrow parallel to the 

 first but not so deep, which is the impress left by the oesophagus. This 

 last impression is very faint on the right lung. This surface also pre- 

 sents the root of the lung, which is situated close behind and above the 

 depression for the heart ; and the hroad ligament of the lung (or liga- 

 menturn latnm pulmonis) already mentioned. In front of the heart, 

 where this surface is applied to the anterior mediastinum, it is narrow 

 and flat. The inner surface of the right lung presents posteriorly a 

 small, semi-detached lobe, not present on the left. The base (or 

 diaphragmatic surface) is concave and moulded on the diaphragm. This 

 surface on the right lung shows the base of the small, semi-detached 

 lobe and the posterior vena cava disappearing into the fissure between 

 that lobe and the main mass of the lung. The apex of the lung is 

 pointed, and lies at the entrance to the chest. The stiperior (or vertebral) 

 border is long, thick, and rounded, and it is lodged in the costo-vertebral 

 groove at the roof of the cavity. The inferior (or sternal) border is 

 shoi't and sharp ; and opposite the heart it is widely notched, a circum 

 stance which allows the pericardium to be tapped at this point without 

 danger of wounding the lung. The notch is smaller on the right side. 

 The posterior (or diaphragmatic) border circumscribes the base, and the 

 greater part of it is included between the periphery of the diaphragm 

 and the chest wall. 



Directions. — The student should now attempt by the following method 

 to restore the lung as nearly as possible to its natural dimensions and 

 relations. The nozzle of a pair of bellows should be wrapped firmly 

 round with a strip of wet cloth until it is made of a convenient size to 

 fit the trachea, which is to be cut across about the middle of the neck 

 for its reception. The nozzle is then to be tied tigVitly into the trachea 

 with a thick piece of string carried several times round, and the lung 

 is to be gradually inflated while an assistant guides it into position, and 

 guards it from being wounded by the cut ends of the ribs. Provided 



