Fibrous Pneumonia is a chronic condition of the lung resulting from long-continued irritation and is characterized by an overgrowth of fibrous connective tissue in the walls of the alveoli. It may be divided into several forms according to its origin: (I) Pneumonokoniosis, those due to the inhalation of irritating particles; (2) those secondary to the acute pneumonias, chronic congestion or atelectasis; (3) pleurogenic, arising from chronic pleurisy; (4) those in which there is peribronchial and perivascular connective-tissue formation.