A morphological study of the lungs and bronchial tree of the dog: with a suggested system of nomenclature for bronchi.

The bronchial tree was investigated in 37 pairs of lungs of adult dogs using dissection and corrosion techniques. The external morphology of the lungs and their lobes has been described. The right lung was divided by deep fissures into four lobes, the apical, the middle, the diaphragmatic and the intermediate. The left lung was found to have three lobes, the apical, the middle and the diaphragmatic. The left apical and middle lobes were partially fused, being separated only by an incomplete (cranial) fissure where either of the two lobes may overlap the other. This study has confirmed the existence in the dog's lungs of 'the stem bronchus' described by Aeby (1880). Each of the lobes of dog's lungs was served by a single bronchus which has been termed the 'lobar stem bronchus' and which extended as an axial stem from the hilus to a particular end of the lobe designated as the 'distal end'. In each lobe two main series of branches and accessory branches have been described. In each main series three types of branches have been described--normal, large, and small. A system of designating the bronchi has been suggested and used. The lobar stem bronchi often bifurcated after a variable number of branches had been given off. The total number of branches arising from the lobar stem bronchus, the number in each main series, the number of accessory branches, and the sequence of origin varied to the extent that no two bronchial patterns were found to be identical. The complexity of establishing a bronchopulmonary segmental pattern in the dog has been discussed.