THORAX AND ABDOMEN OF THE HORSE 



19 



that is, the point of attachment of the root. Behind the hilus there is 

 a triangular area uncovered by pleura ; or, in other words, the two 

 layers (dorsal and ventral) of pleura that form the pulmonary ligament 

 gradually separate more and more as the hilus is approached. The 

 right and left lungs are closely adherent to each other over this 

 uncovered area. Dorsal to the hilus and the attachment of the 

 pulmonary ligament there is a longitudinal groove produced by the 

 oesophagus ; and still more dorsal another groove, curved for the 

 accommodation of the aorta, may be noticed, especially on the left lung. 

 On the right lung the most cranial (curved) part of the aortic groove is 

 replaced by one, also curved, for the vena azygos. 



Groove for CEsophagus. 



I 

 Dorsal border 



Bronchus. 



i Groove for aorta. 



I 



I ! 



I ! 



Groove for deep cervical 

 I and costo-cervical 

 venous trunk. 



Cardiac impression. 

 Cardiac notch. 



Diaphragmatic surface. 



Line of reflection of pleura 



A. pulmonalis. 



Vv. pulmonales. 

 Fig. 7. — Medial aspect of the left lung. 



Cranial to the hilus are grooves for the reception of the trachea, and 

 the common brachio-cephalic trunk and cranial vena cava, and their 

 branches. 



The intermediate lobe forms a prominent projection on the media- 

 stinal surface of the right lung. 



The dorsal border (margo dorsalis) of the lung is adapted to the 

 channel formed by the ribs and the bodies of the thoracic vertebrae, and 

 consequently is comparatively thin at the apex, but becomes thick and 

 rounded towards the base of the organ. 



The ventral border (margo ventralis) is much shorter and thin 

 throughout. It occupies the narrow space (sinus costomediastinalis) 

 between the ribs and the mediastinal septum, and is notched for the 



