The mortality of typhoid and of diphtheria is being reduced toward the vanishing point, but the mortality per hundred thousand of population for pneumonia remains about as it was before the advent of modern investigation. The causative factors have been studied and endeavors have been made to use combative methods common to infectious diseases. Recent studies prove that the avenue of approach may have been wrong.
The observation has been made in operative cases that pneumonia occurs with occlusion and collapse of the lung, especially noticeable in abdominal cases, in which breathing is impeded by pain. This collapse, atelectasis or apneumatosis (Coryllos), precedes postoperative pneumonia and gives it the characteristics of occlusion and undrained infection. Occlusion prevents such natural protective devices in the lungs as the reflex cough, aimed at the removal of foreign bodies, and the movement of respiration which is properly accompanied by peristaltic contractions and relaxation of