There is a very large group of persons in which a positive diagnosis of pulmonary tuberculosis has been made erroneously on insufficient and inconclusive evidence. Some of these diagnoses have been based on suggestive histories and suspicious symptoms, others on physical signs which are entirely normal, with or without supportive evidence in history or symptoms. Physicians are prone to confirm a diagnosis of tuberculosis, faulty or not, in any patient who has previously been declared tuberculous, perhaps through doubt of their own diagnostic ability, perhaps through fear of erring on the wrong side, perhaps, when former physical findings are corroborated, on the mistaken assumption that a once manifest tuberculosis must forever after leave signs evident on physical examination. In any case, these mistaken diagnoses are almost invariably supported by descriptions of nonexistent or misinterpreted physical signs.
It goes without saying that the earliest possible diagnosis is highly desirable; but, on