The importance of pulmonary tuberculosis as a cause of death in Wales has been the subject of much consideration. Many of the investigations, however, have been of a definitely local character, though this fact does not detract from their merit as is evinced by the work done by Wade, Bowen and the King Edward VII Welsh National Memorial Association. For a really comprehensive study we are indebted to the late Dr Brownlee. His contribution to the epidemiology of phthisis was unique in its suggestiveness. He postulated the theory that phthisis as a disease was, not an entity, but that it consisted of three types—“Young Adult,” “Middle Age,” and “ Old Age,” corresponding with separate strains of the infecting bacillus. According to his conception the great bulk of the phthisis deaths in Wales was due to early or late types of the disease. He reached this conclusion from a study of the pulmonary death-ratesof males between 1851 and 1870 in the registration districts of Wales.