The medical profession has long been familiar with the fact that many persons have tuberculous lesions of the lungs which appear, regress and heal without ever giving rise to symptoms or physical signs. Only recently has this fact assumed significance for the practitioner. Formerly asymptomatic tuberculosis passed undetected until, in the course of postmortem examinations, these old healed lesions were revealed to the pathologist. The clinician's experience was limited to frank clinical tuberculosis because diagnostic methods were not sufficiently refined to reveal minimal lesions.
Today roentgenology has developed to the point at which some of these symptomless lesions are visualized from the time of infection to complete healing. As a result the clinician now has evidence of both (a) the preclinical stages of early tuberculosis and (b) the asymptomatic lesion which will heal without ever giving rise to clinical disease. The lesions of clinical tuberculosis appear in less than 2