THE LUNGS 



533 



The ventral border (Margo ventralis) is thin and short; it occupies the angular 

 space betweeri the mediastinum and the ventral parts of the sternal ribs (Recessus 

 costo-mediastinalis) . It presents, opposite to the heart, the cardiac notch (Incisura 

 cardiaca). On the left lung this notch is opposite to the ribs from the third to the 

 sixth, so that a considerable area of the pericardium here lies in direct contact with 

 the chest-wall. On the right lung the notch is much smaller, and extends from the 

 third rib to the fourth intercostal space. 



/ .JHo^®^* cardiac notch is usually quadrilateral; its highest part is about four to five inches 

 (cii. 10-12 cm.) above the sternal ends of the fourth and fifth ribs. The right notch is usuaUy 

 triangular; its apex is about three inches (ca. 7-8 cm.) above the level of the sternal end of the 

 ribs at the third intercostal space. In some cases a fissure partially marks off the apex from the 

 body of the lung. 



The base of the lung (Basis pulmonis) is oval in outline; its surface (Facies 



Bronchial artery 



! Bronchus 



Pulmonary / ; Pulmonary 

 Ligament of lung (cut) 



Line of rejlectum 

 of pleura 



Fig. 47.5. — Left Lung of Horse; Mediastinal and Diaphragmatic Surfaces. 

 Organ hardened in situ. Vascular impression for- common dorso-cervico-vertebral vein. 



diaphragmatica) is deeply concave in adaptation to the thoracic surface of the 

 diaphragm. Laterally and dorsally it is limited by a thin convex basal border 

 (Margo basalis) which fits into the narrow recess (Sinus phrenico-costalis) between 

 the diaphragm and the lateral chest-wall. The position of this border, of course, 

 varies during respiration. In the deepest inspiration it may reach the bottom of 

 this recess. 



Indissecting-roomsubjects the distance between the border and the diaphrag- 

 matic line of reflection of the pleura increases from about two inches (ca. 5 cm.) at 

 the seventh rib to about six or seven inches (ca. 16-18 cm.) at the fifteenth, and 

 then decreases. The dorsal end of the base is usually at the vertebral end of the 

 sixteenth intercostal space or seventeenth rib.^ 



The apex of the lung (Apex pulmonis) is prismatic, narrow, and flattened 

 transversely. It is partially marked off from the rest of the lung by the cardiac 



' The ventral and basal borders may be taken together under the term margo acutus. 



