THE HISTOLOGY OF GENERALIZED PULMONARY EMPHYSEMA

SUMMARY The evolution of morphological changes in the air passages from the early focal lesions of emphysema to those associated with the clinical disease is presented. Progress of the focal lesions leads to involvement of the whole of the secondary lobule, at which stage the emphysema is no longer focal but “diffuse”. This diffuse change occurs at different stages of development of the focal lesions in different lungs ; the morphological evolution of both early and late change is described along with some of the more common intermediate forms. Observations supporting the hypothesis of pathogenesis of emphysema presented in Part I of this paper have been made, and the hypothesis is extended to account for diffuse change. These diffuse lesions are aggravated by bronchospasm and, relatively late in the morphological evolution of the disease, by expiratory collapse of bronchioles. The emphysematous changes themselves, in turn, aggravate this last factor. The hypothesis of pathogenesis is reviewed, and morphological evidence is correlated with several aspects of physiological observations on alterations of lung function in the disease. The relation of chronic bronchitis to emphysema is analysed in view of these observations, and it is concluded that chronic bronchitis cannot be said to “cause” emphysema, but, rather, both are related by way of the common factor of inflammatory disease of the bronchioles.