But from this lobular development of the infiltration we cannot at the bedside conclude that any pneumonia is of the catarrhal variety or a bronchopneumonia. Similar characteristics are not rarely present in the croupous forms.

Regarding the occurrence of such lobular croupous pneumonia in influenza there has been for a long time no doubt. We early called attention to this form. Birch-Hirschfeld has, as we have previously seen, divided croupous influenza pneumonia statistically into lobar and lobular forms. (Compare p. 613.) This is not peculiar to influenza. The rare croupous pneumonia of measles, diphtheria, and whooping cough regularly shows a lobular structure. Strumpell especially mentions the "lobular croupous pneumonia" in measles, but even the every day genuine lobar croupous pneumonia by no means always affects the entire lobe at one time. The pathologist most often sees the whole lobe affected, but cases are common in which, besides a completely infiltrated lobe, partly lobar or lobular fibrinous areas in other lobes are found postmortem. With the clinician who is able to note the course of genuine croupous pneumonia step by step it is a frequent experience that the genuine croupous pneumonia gradually and slowly makes its way over the entire lobe, affecting at first the dorsal portion, and the ventral part either much later or not at all, especially in apical pneumonia. The clinical form of pneumonia migrans ascendens and descendens frequently occurs in one and the same lobe of lung.

Of interest are those cases in which in the same lung, or even in the same lobe of a lung, fibrinous areas of a different age, red and gray hepatization, are found close together. Such a hepatized lobe shows very plainly the lobular composition of croupous pneumonia. In our influenza lectures we have called attention to some instances of this kind.*

"Thus, for example in one case we found, in the center of the left lower lobe, which had undergone red hepatization, a wedge about the size of a lemon, of yellowish gray color, and granular surface; a focus cut off by a perfectly sharp border from the surrounding red hepatized portion."

The remarkably slow development of croupous pneumonia in influenza is also shown by the fact that we occasionally find, when death takes place late (about the seventh day of pneumonia), the affected lobe in a condition of firm red hepatization. A. Vogl emphasizes the same fact.

In one case affecting a young man aged twenty two we performed the postmortem upon the ninth day of a double lobar croupous influenza pneumonia which was bilateral from the commencement. We expected, on account of the course and duration of the affection, to find gray hepatization, but were surprised to find a fresh, brownish red hepatization of both lower lobes (microscopically, fibrinous pneumonia with marked hyperemia).**

On the other hand, occasionally a rapid change of croupous pneumonia into the stage of gray hepatization and mucopurulent softening is found. We have observed this as early as the third clay of pneumonia. A. Vogl found, on the fourth day, " already purulent change of the fibrinous exudate." In reference to these cases we remarked in December, 1889: " the gray, mucopurulent softening of a hepatized lobe as early as the third day of pneumonia is a remarkable condition, and is probably due to the fact that croupous influenza pneumonia is often characterized from the beginning by a copious infiltration of leukocytes into the alveolar lumina and interstitial parts of the lung."

"The lung of a patient dying of this affection on the ninth day of influenza, that is, on the fifth day of the pneumonia, showed a very remarkable picture. The left lower lobe was large; its pleura covered with a thin, fibrinous membrane; the lobe upon section showed a variegated surface, consisting of dark red, flat infiltrates alternating with gray, markedly granular areas having the typical appearance of yellowish gray hepatization. The dark red areas were also devoid of air. The right lung was, with the exception of the upper part of the upper lobe and a small part of the anterior border, absolutely airless, infiltrated partly with red and smooth and partly gray red and gray granular exudation. The right lower lobe on section showed a gray, granular surface. Therefore, here again we had gray hepatization upon the fifth day of pneumonia, with lobular mixed infiltrates of variable appearance."*

* Loc. ext., pp. 42, 43, and 50.

** Influenza lectures, p. 47.

We must mention also the cases in which lobar influenza pneumonia runs a protracted course, so that, after the crisis has occurred, with a normal temperature or with the continuance of an intermittent or remittent fever, the lobar infiltration, with complete dulness and pure bronchial respiration, remains without redux crepitation and without rales for a week or even longer.

"With such slowly absorbed infiltrations, especially in the lower lobe, we have often been in doubt as to the diagnosis, whether an infiltration or an exudate were present, until the aspirating needle confirmed our assumption of the presence of an infiltration." In several cases of protracted pneumonia lasting for weeks with intermittent fever, especially with a hereditary history and when an upper lobe was the seat of the pneumonia, we suspected tuberculosis, until complete resolution removed the suspicion. In such cases of delayed resolution the purulent and blood streaked sputum outlasted the acute stage of pneumonia.

Such influenza pneumonias are, as clinical and pathologic statistics ** show, frequently multiple (in our statistics, 60 per cent, of the cases), and very often are also bilateral from the beginning. We emphasize the expression "from the beginning," for it is well known that a genuine croupous pneumonia may frequently migrate to the opposite side (pneumonia ascendens, descendens, saliens, migrans, cruciata). Occasionally in bilateral pneumonia the inflammation of one side would affect the whole lobe, while the other side remained lobular-that is, partially lobar-during the whole course.