Abstract
Twenty rabbit lungs were examined. The right and left bronchi give of four bronchiole systems, i.e. the dorsal, lateral, ventral and medial. The cranial lobe is formed by the first bronchiole of the dorsal bronchiole system. The middle lobe is formed by the first bronchiole of the lateral bronchiole system, and the accessory lobe is by the first bronchiole of the ventral bronchiole system. The remaining bronchioles of the four bronchiole systems constitute the caudal lobe. Accordingly, the right lung consists of the cranial, middle caudal and accessory lobes, and the left lung consists of a bi-lobed middle and caudal lobes. The right pulmonary artery runs across the ventral side of the right cranial lobe bronchiole. Then it runs across the dorsal side of the right middle lobe bronchiole. Thereafter, it runs along the dorso-lateral side of the right bronchus. During its course, it gives off arterial branches, running along the dorsal or lateral sides of the bronchioles. The left pulmonary artery runs across the dorsal side of the left middle lobe bronchiole. Then it runs the same course as in the right lung. The pulmonary veins mainly run the ventral or medial side of the bronchioles or between the bronchioles. Finally they enter the left atrium with large four veins.
