It has recently been suggested that in the central eastern region of the United States there is a disease or a group of diseases which closely simulates tuberculosis. This has been indicated by the observation of pulmonary calcification in persons who are negative reactors to tuberculin but in whom the reaction to histoplasmin is positive. Until the past decade pulmonary calcification in the presence of a negative reaction to tuberculin has been considered a manifestation of a disturbance of the allergic mechanism, but the more probable explanation is that there is another disease or group of diseases which account for many instances of pulmonary calcification. That this is a likely possibility is demonstrated by the striking similarity in some instances of coccidioidomycosis to tuberculosis during the active and the end stages of disease.
Christie and Peterson1 and Palmer2 have shown a correlation of sensitivity to histoplasmin with pulmonary