The lungs (Figs. 342, 343) differ in shape from those of the horse and
ox in conformity with the shape of the thorax, which is relatively very
wide in the dog; the lateral thoracic walls are strongly curved, and the
costal surface of the lungs is correspondingly convex. There is no
cardiac notch on the left lung, although a small part of the pericardium
is not covered by the lung at the lowest part of the fifth and sixth
intercostal spaces. On the right side the cardiac notch is opposite the
fourth and fifth intercostal spaces. Each lung is divided by deep
fissures into =three lobes=—=apical=, =cardiac=, and =diaphragmatic=;
the right lung has in addition a =mediastinal lobe=. The apical lobe of
the right lung is considerably larger than that of the left. The latter
is often more or less fused with the cardiac lobe. Variable accessory
lobes may be found. On account of the small amount of interlobular
tissue the lobulation is not distinct.