THE LUNGS 533 
The ventral border (Margo ventralis) is thin and short; it occupies the angular 
space between the mediastinum and the ventral parts of the sternal ribs (Recessus 
eosto-mediastinalis). It presents, opposite to the heart, the cardiac notch (Incisura 
eardiaca). 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. 
The left cardiac notch is usually quadrilateral; its highest part is about four to five inches 
(ca. 10-12 cm.) above the sternal ends of the fourth and fifth ribs. The right notch is usually 
triangular; its apex is about three inches (ca. 7-8 em.) 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 
t 
| Bronchus 
I / 
Pulmonary | | Pulmonary Vascular 
! / rt py - 
' artery impression 
Ligament of lung (cut) veins 
"Ds avy 60 
/ 
Line of reflection 
of pleura 
Fic. 475.—Lerr Lune or Horse; MEDIASTINAL AND DIAFHRAGMATIC 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. 
In dissecting-room subjects the distance between the border and the diaphrag- 
matic line of reflection of the pleura increases from about two inches (ca. 5 em.) at 
the seventh rib to about six or seven inches (ca. 16-18 em.) 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 
1 The ventral and basal borders may be taken together under the term margo acutus. 
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