Cancer of the lung seems unmistakably to be steadily increasing in frequency. This increase, both relative and absolute, cannot be explained as being solely due to improvement in diagnostic technic and to more careful postmortem studies. Accurate descriptions may be found in the writings of Rokitansky, Virchow, Laënnec, Graves and many others. Whereas older clinicians regarded it as rare, it has in the past two decades come to occupy a place second in importance only to such common localizations of malignant growths as the stomach, the uterus and the rectum. This fact has been emphasized in England, in the United States and to an even greater degree in central Europe. The incidence, as cited in recent statistical reports, varies between 5 and 10 per cent of all cancers.
Among the contributing factors to this increase, the injurious effects of tobacco smoking, exhaust gases from automobiles, tar on roads and the