This section is from the book "A Manual Of Pathology", by Guthrie McConnell. Also available from Amazon: A Manual Of Pathology.
Hemorrhage From The Lung, or hemoptysis, occurs in many conditions - trauma, embolism, etc. - but is most common in phthisis, particularly in the later stages when ulceration has taken place. The blood may be expectorated or part of it may enter portions of the lung. These areas do not contain air, are dark in color, and resemble splenic tissue.
Hemorrhagic infarction is merely a localized hemorrhagic area following obstruction of the arteries by emboli. It will not occur, as a rule, unless passive congestion or some other circulatory interference is present. The area is usually just beneath the pleura with its base circumscribed and directed outward, the apex directed toward the hilum; is dark red, almost black in color, dense and airless. The air-spaces and the inter-alveolar tissues are filled with erythrocytes and some fibrin. Infarcts may be small or large, single or multiple. If infection does not take place the tissues may regain their normal condition. Usually there is degeneration with subsequent cicatrization, an irregular depressed scar resulting.