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Medicine is not and cannot be an exact science because of the complexity of the human element involved. Roentgenology is the youngest branch of the specialties and is a study of living pathology. Even pathology is subject to many changes through experience, progress in investigation and study. This is one of the factors concerned in changes in roentgenology, and presumably for its betterment, through greater exactitude, further investigations, added experience and the acknowledgment of and correction of mistakes. In 1924, when a group of roentgenologists were on trial for possible acceptance as a new section in the American Medical Association, I presented a paper1before the Section on Miscellaneous Topics, in which were reported three cases of what seemed to be a new entity among intrathoracic tumors. I have selected this subject again for the chairman's address as one slight means of showing that roentgenologists are genuinely alive to
Henry K. Pancoast (Sat,) studied this question.