=Gray Hepatization=, which characterizes the third stage of pneumonia, is known by the lung presenting a firm, semi-solid, inelastic, and more or less incompressible character. Failing to collapse, the lung is found more or less completely filling the chest. The pleura will generally present evidences of inflammation in the presence of patches of lymph and more or less points of adhesions. The upper lobe may be soft and compressible, while the lower is solid from hepatization. When divided with the knife, the substance is found of a gray, red, or dirty yellow color; compact, but friable and easily broken down with the fingers, while the smaller bronchial tubes are filled with fibrinous plugs. Bloody purulent matter, with much turbid serous fluid, will ooze from the cut surfaces. Pus globules will be detected in the escaping fluids by a microscopic examination. _Resolution_ of a hepatized lung, consists in the gradual softening of the effused substances within the smaller bronchial tubes and air cells, and the discharge of the same by cough and expectoration. Inflammation of the lung usually commences in the lower lobe, and while the disease here may extend to complete hepatization, the middle lobe may be found merely congested, while the upper is quite healthy. Inflammation may attack one or both lungs. In the former case it is known as single, and in the latter as double pneumonia. From an examination of a large number of cases, it has been ascertained that inflammation of the right lung is more frequent than that of the left in the proportion of about three to one, and that single pneumonia is more common than double pneumonia in the ratio of six to one. Pneumonia is sometimes divided into _Catarrhal_ and _Croupous_. In the former, the exudation contains little or no fibrinous matter, while the bronchial mucous membranes are also involved, the disease at the same time being confined mostly to the lobules of the lungs. In the _croupous_ form, the exudation contains a large proportion of fibrine, and the disease usually involves the greater part of a lobe, or may extend to the whole of one or both lungs. Both forms of the disease may run through the three stages of congestion, red and gray hepatization. A peculiar form of inflammation of the lungs, found mostly in children and young persons, and usually chronic in character, has been described as _Lobular Pneumonia._ The inflammation here being confined to the lobules, these, after the disease is perfectly developed, present the appearance of a multitude of rounded nodules, of the size of small nuts, scattered through the substance of the lungs. The exterior of these is reddish, firm, and vascular, while the interior is of a grayish color, containing effused lymph, with more or less purulent matter.