While the symptomatology of pneumonia has been thoroughly worked out, and the disease is viewed as infectious by those most competent to judge, there remains yet some diversity of opinion as to the relations between the varieties designated respectively croupous or lobar and catarrhal or lobular. Pneumonia is no longer considered the pulmonary localization of a constitutional disorder, but rather a true inflammation of the lung, dependent, as experience has shown, upon a variety of causes. While the essential and the final cause is some low form of vegetal life, we have learned that the active bacterium is not always the same and that its mere presence is not sufficient to constitute or initiate the disease-process. On the contrary, certain conditions must have been previously fulfilled in order that the activity of the microörganism shall be expended in a specific direction.
Pneumonia in adult life differs from the same disease