An account of the longitudinal mucosal corrugations of the human tracheo-bronchial tree, with observations on those of some animals.

A description is given of the distribution of the longitudinal mucosal corrugations in the human tracheo-bronchial tree. It has been shown that they are made up of elastic tissue in a collagen matrix, and that the elastic fibres continue into the smallest bronchioles beyond where the corrugations are no longer visible. An examination has also been made of the tracheo-bronchial trees of the hen, rat, raccoon, pig, sheep, llama and tiger. Corrugations are present in all these animals, except the hen and the raccoon, and they have been compared and contrasted with the condition in Man. The functional significance of these corrugations remains unknown, but, they could be important in equalizing tension in the tracheo-bronchial tree during inspiration, as well as in providing elastic recoil during expiration.