We have reported in the past obstructive emphysema and atelectasis in acute respiratory disease of infants.1 We believe that the same reactions take place in influenza and offer a rational explanation for the dynamics of the pathologic changes, x-ray appearances and clinical course. Our work is based mainly on x-ray studies over a period of years at Harlem Hospital, where annually more than 500 cases of pneumonia are seen from Dr. J. G. M. Bullowa's service alone. As far as we have been able to determine, W. G. MacCallum is the only one in this country who has promulgated such a theory, which he based on observations made at autopsy.
The presence of emphysema of the lungs in influenza was recognized by pathologists for many years, especially during the World War.Wolbach2 described in 1919 a striking emphysema of the alveoli best seen under the pleura. At