Acquired pulmonary syphilis is exceedingly rare pathologically, and it is even more rare as a clinical picture. In congenital syphilis, it is a not infrequent pathologic picture in the form of the well known white pneumonia. As a diffuse sclerosis and as small gummas, it is also encountered clinically, and subsequently it is encountered as a pathologic picture in the congenital form of the disease. As in syphilis of the gastro-intestinal system, in which the symptomatology is so like that of other gastro-intestinal disease, so also in lung syphilis we are dealing with a condition in which clinically there is absolutely no diagnostic picture. In its various forms, syphilis of the lung may present itself with a clinical picture of any phase of pulmonary disease. For this reason, the condition probably exists to a greater extent than is indicated by either the clinical or the pathalogic reports. OBSERVATIONS TO THE