104 THE ANATOMY OF THE HORSE. 



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

 The intei-nal (or mediastinal) surface is moulded on the mediastmum 

 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 posterior 

 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 presents 

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

 depression for the heart ; and the h-oad ligament of the lung (or hgamen- 

 tum latum pidmonis) already mentioned. In front of the heart, where 

 this surface is applied to the anterior mediastinum, it is naiTOw and fiat. 

 The inner surface of the right lung presents posteriorly a small, semi- 

 detached lobule, not present on the left. The base (or dia]}hragmatic 

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

 right lung shows the base of the small, semi-detached lobule, and the 

 posterior vena cava disappearing into the fissure between that lobule 

 and the main mass of the lung. The ajxx of the lung is pointed, and 

 lies at the entrance to the chest. The superior (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 short and 

 sharp; and opposite the heart it is widely notched, a circumstance 

 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 diap/a-agmatic) 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 tightly 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 

 the lung has not been injured, it can by this means be restored to its 

 natural position, and the student should then observe the area of 

 pericardium which is left uncovered at the notch in the lower border. 

 The right side of the chest may next be opened, making the same 

 incisions as on the left. On raising the base of the right lung from 

 the diaphragm, its supernumerary lobule will be seen, and also the 

 posterior vena cava and right phrenic nerve invested by the special fold 

 of pleura. The right lung may then be inflated, and the extent of 



