Size-independent distribution of bronchial cartilage in four species of myomorph rodents

The size-independent distribution of bronchial cartilage in the conductive bronchial tree of four species of myomorph rodents different in body weight was determined by the inspection of translucent cartilage-stained whole-lung-specimens in comparison to bronchial casts. The lungs of the harvest mouse, Micromys minutus, body weight 5-7 g, the laboratory house mouse, Mus musculus, body weight 35-45 g, the laboratory brown rat, Rattles norvegicus, body weight 200-400 g, and the African giant pouched rat, Cricetomys gambianus, body weight 1200-1800 g, shaw the same lobulation and ramification of the conductive bronchial tree. All four rodents possess dorsally open cartilaginous braces in the trachea and in both main bronchi up to the first ventral branch of the left lung or to the emerging bronchus of the right middle lobe. The distribution of cartilage tissue in the bronchial tree of the four species investigated is identical and shows no relation to the size of the lung or the bronchi. The definition of the term "bronchus" by the presence of cartilage is criticized and the function of intrapulmonary bronchial elements is discussed.