Inflammation is characterized by a greater solidity and increasing softness of the lung-tissue: characters which are unreliable except as questions of degree. The most important points of distinction are the loss of capability of insufflation, the opacity of the tissue, and its duller white color, which is frequently granular on scraping or section, or, if not granular, has a rougher appearance than the sec tion of a simply collapsed part. If the inflammation has reached the surface, the implication of the pleura is a further distinction. The area of these spots varies, and sometimes the inflammatory change may be found scattered through a collapsed and congested part. They yield a milky juice on scraping or press ure, due to an epithelial proliferation in the interior of the alveoli, mingled with leucocytes which have probably escaped from the vessels. The amount of fibri nous exudation is, however, relatively small. Nodules of pneumonic change, probably proceeding by direct extension from the bronchi, may be found in the midst of collapsed portions without the intervention of congestion and cedema.
Lobular pneumonia thus frequently proceeds indirectly from lobular collapse. It arises also directly in the vesicular structure by extension from the bronchi. The nodules of vesicular pneumonia may vary in size from a pin's point to a hemp seed, or they may be so small as only to be recognized by the microscope. At first the spots may have the dark-red color of the ordinary acute form, but they tend to pass rapidly into a dull yellowish, opaque-white color, which has a finely-granular aspect. They are not markedly prominent, and they fade insen sibly into the surrounding tissue, though when occurring in the midst of collapsed lung they stand out distinctly from the dull-purple ground on which they are situated. They are soft and easily broken down, and yield a milky juice on scraping or pressure. The nodules tend to be come confluent, and may sometimes form racernose groups, but these are less dis tinct and less sharply defined than those of tubercle. Their histological structure is identical with that of areas of lobular collapse, viz.: an epithelial proliferation mingled with leucocytes which fill the alveoli.
Balzer has described another process by which the lung is affected from the bronchi, viz.: by direct extension of the inflammation from the bronchial wall to the surrounding pulmonary tissue, which he regards as the most common form.
More diffused forms of pneumonic consolidation are found in some in stances, and particularly in measles. It is probable that some of these arise from secondary inflammation of collapsed por tions; others may arise from the con fluence of lobules primarily affected, but it is possible also that a more diffuse inflammation may, in some cases, directly attack the lung without the intervention of either of these processes, and through the immediate effect of the poison of the primary disease.
The very varied proportions in which bronchial dilations and collapse and gen uine pneumonic consolidation occur in different cases of capillary bronchitis— variations which are, in part, due to the diseases in which they severally originate —have led some authors to deny that a genuine pneumonia is present in these cases, and in some instances but little can be found post-mortem beyond the two first-named conditions. A genuine bron cho-pneumonia does, however, occur.
The collapse which occurs in many ex hausting diseases may lead to secondary pneumonia in the same manner as it does in the bronchitis of childhood. In many cases only congestion and spleniza tion occur, but in others a true pneu monia presenting a striking resemblance to that of childhood is found.
extravasations into the lung are not uncommon, and are mostly subplenral and petechial, but may be more extensive.
Emphysema almost constantly accom panies broncho-pneumonia. It affects mainly the upper lobes, especially their anterior margins. This emphysema is sometimes termed "compensating," and is believed by some to originate in the lung expanding to occupy the areas be tween the collapsed portions. It is, how ever, more probably due, in part, to cough and, in part, to inspiratory effort, resembling that found in acute asphyxial conditions. Interlobular emphysema is not uncommon in fatal cases of whoop ing-cough at early ages.
The disease almost invariably affects both lungs. The amount and character of the affection may vary greatly on dif ferent sides: on one, collapse or diffuse pneumonia may predominate; on the other, pneumonia may be lobular and the amount of collapse small.
In the further progress of broncho pneumonia there is little doubt but that in many cases a perfect restitutio ad integrant may occur, and that the lung may regain its normal condition. In other instances, however, dilated bronchi may long persist, with some condensation of the pulmonary tissue surrounding them, but may gradually return to the normal state, so far as may be judged of from the physical signs. Abscesses oc casionally form, though usually they are small in size, and gangrene is sometimes observed in the affected portions. In rarer instances general consolidation of the lung may remain in a chronic form. In some instances the pneumonic nod ules, particularly in scrofulous and rick ety children, may pass into cheesy changes, with destruction of tissue, and may rim the subsequent course of tuber cle. In some instances the process is tuberculous from the beginning.