There appears to have been a striking increase in the number of cases of cancer of the lung during recent years in America and Europe. That this increase is not altogether the result of greater precision in diagnosis is evident when we consider that not only clinicians have noted it, but also pathologists have reported to this effect. Douglass Symmers has observed this increase in the pathologic laboratories of the Bellevue Hospital in New York, and Hampeln,1 Staehelin,2 Assmann,3 Berblinger,4 Holzer,5 Heilmann,6 Kikuth,7 and others in Europe have published statistics to this effect. The problem to be cleared up by those engaged in cancer research is whether this goes hand in hand with the increase in visceral cancer recently observed in civilized countries or there is some special etiologic factor operative in the case of the lungs, such as dust in modern industrial centers, as noted by Hampeln,1 Heilmann6 and