The well developed post-mortem muscular rigidity, the lividity of the dependent parts, of the face with its mucous membranes, and often of the trunk, the jaundice variable in extent, the crusts of blood on the nares and mouth, and the splanchnic dilatation are features which prepare for the gross picture presented by the thoracic organs. The increased moisture within the pleural cavities associated with the even, translucent pleural surface, whose dilated lymphatics become more and more prominent towards the hilum, the large succulent lymph glands, and the exudate in the bronchial tree, are all striking, but more characteristic of the gross picture, is the great increase in volume of the lung itself, mottled with brilliant colors. The lung, too, is very wet and on section, after the syrupy, blood-stained fluid escapes from the less definitely consolidated zones, the latter appear, not as the usual granular, firm areas of hepatization, but have more the consistency of a gel, and also its translucence. Characteristic of this disease as these changes may be, the specificity of the fundamental lesion in the respiratory tract, becomes more emphatic after study of its histology (92, 162). _Histological Picture._ No matter what the portion of the lung from which the sections are derived, the fundamental changes found are the same. The subpleural sheets are spread wide apart, now by empty spaces, now by coagulated fluid. The process extends from the surface through the interlobular septa (Fig. XX), and is accentuated where the connective tissue is more prominent around vessels and bronchi. The nature of the infiltrate in the subpleural and interstitial tissues becomes more evident in the alveoli, which likewise are filled. The material varies somewhat in appearance, probably dependent upon its proteid content. Not infrequently the alveoli contain a homogeneous, pink-staining mass, which resembles the colloid of the thyroid gland. Again, it may be simply a coarse granular precipitate (Fig. XXIII), and in still other instances, small sticks and strands form the bulk of the alveolar content (47, 92, 140, 156). This subpleural, interstitial, perivascular, peribronchial, and alveolar edema, which is a term applicable to this collection of fluid, is very prominent, and although its intensity varies in different portions of the lung; and although it may be replaced in some areas by other types of exudate, unquestionably, this is the dominating expression of the inflammatory process in the early stage of the disease.