Although the value of the roentgen-ray examination of the lungs is now firmly established as an indispensable step in the early diagnosis of tuberculosis, its greater value in the determination of prognosis and management is still generally unrecognized.
As a rule, every pathologic change occurring within the lung causes a variation in the relative density of the area involved. Through the agency of serial roentgen-ray examinations it is possible to follow these changes step by step, and thus finally to classify each case as (1) progressive, (2) regressive or (3) arrested.
Without the control of periodic roentgenologic observations, it would be necessary to place in a sanatorium all cases of pulmonary tuberculosis giving clinical evidence of activity. With adequate control, however, this expensive procedure becomes unnecessary and at times reprehensible.
I have observed many cases, over long periods, in which the lesions as seen roentgenologically remained essentially unchanged, despite the