Together with the hyperemia just described, an edema of the lungs, like the ordinary passive edema, which we often see in croupous pneumonia in the uninfiltrated lung (foaming edema, fluid contain ing air), exists. In other cases, besides the general hyperemia, there may be a localized edema of the lung or a lobe of quite a different character and importance. The affected lobe is large and heavy. It feels floppy; its cut surface is smooth, of a moist, mucoid appear ance, and of a brown red or gray red color. The lobe is frequently almost devoid of air; the expressed edematous fluid is turbid and contains scarcely any air bubbles. This condition is called "edematous infiltration," "infiltration pseudo oedemateuse," or "serous pneumonia."
That this condition is really due to inflammatory processes (" inflammatory edema ") is shown by the fact that now and then in such an affected lobe several areas are found which have a firmer consistence and a more finely granular appearance (serofibrinous pneumonia), and also not infrequently the pleural covering of the affected lobe is cloudy and rough, and covered by a fine fibrinous membrane.
The sputum of influenza pneumonia in a majority of cases shows all those characteristics which we have already mentioned in describing influenza bronchitis, especially the copious serous, foamy sputum, often blood streaked, and the purulent mvmmular sputum, or even sputum globosum. (Compare p. 605.) The latter is often present from the onset of the pneumonia; occasionally it is dotted or streaked with blood. From the purulent character of the sputum many observers were accustomed to diagnose a catarrhal pneumonia. This is certainly a mistake, for numerous cases, confirmed by autopsy, of croupous influenza pneumonia have taught us that the typical sputum croceum is but rarely found, the purely purulent sputum being far more common. This is due to the fact that the diffuse purulent influenza bronchitis accompanying the pneumonia decides the character of the expectoration and does not permit the pneumonic sputum croceum to make its appearance. This is well known in genuine croupous pneumonia attacking patients with chronic bronchitis and bronchorrhea, emphysema, bronchiectasis, etc.
The symptom complex of influenza pneumonia is differentiated also in many other respects from typical pneumonia. The patient suffering from the combined diseases presents a composite picture.
The distinctive features are the general or papular redness of face, particularly on the forehead, nose, and around the eyes, the profuse sweating from the beginning of the attack, the spasmodic paroxysms of coughing peculiar to influenza; all these are symptoms which do not generally arise in a genuine pneumonia.
So far as the temperature is concerned, the fever curve generally rises abruptly with the pneumonic attack, and remains at a high level. In a gradually developing pneumonia the rise of temperature also occasionally takes place gradually. The intermittent and recurring pneumonias previously alluded to have corresponding temperature curves. The rise of temperature is frequently quite disproportionate to the extent of the pneumonia and the gravity of the attack.