Diameters of bronchi at asymmetrical divisions.

The weight, and hence volume, of a cast of the bronchial tree of a sheep distal to any point was found to be a function of the diameter of the bronchus at that point. This result has been used to derive a relationship between the diameter of a bronchus and the diameters of its branches which is applicable to different types of branching and is consistent with principles of minimum energy loss within the bronchial tree.