The mortality tables of all countries agree in showing considerable rise in the mortality from pulmonary tuberculosis in influenza periods. With this fact the observation of every clinician agrees,* that the course of tuberculosis of the lungs is markedly and unfavorably influenced by influenza and its pneumonic complications. Latent quiescent cases of tuberculosis became active; "healed" or healing foci broke out anew; afebrile cases were changed to the hectic type or to cases of acute "phthisis florida," and frequently hemoptysis was induced. The influenza bacillus, as Pfeiffer has remarked, prepares the way for a further invasion of the lungs by the tubercle bacillus. The same author found that the lungs of tuberculous patients form an especially favorable influenza soil, so that they grow and multiply on it for weeks and months; this has been termed the " chronic influenza of tuberculous patients." Nevertheless numerous phthisical patients have recovered not only from simple ' uncomplicated influenza, but also from influenza complicated by lobular and lobar pneumonia, as easily as other patients. Two facts are worthy of special note, namely: (1) That advanced phthisis, which, as a rule, gives a considerable degree of immunity toward acute infectious diseases, did not confer any immunity against influenza; and (2) that even advanced phthisical patients affected by influenza not rarely acquired lobar croupous pneumonia, which, apart from the presence of influenza, is extremely rare in phthisis.** It was often asserted that phthisical patients showed special pre disposition to influenza; Pfeiffer's results, just quoted, lend color to this view. H. Rieder has represented me as its chief exponent, but incorrectly, because already in my lectures of 1890 I said that " the figures available to support this view are too few for such a conclusion." The greatly increased death rate from tuberculosis in influenza periods merely indicates a higher mortality, not a higher morbidity.
* Compare P. Friedrich's instructive tables, loc. ext., p. 197. ** Influenza lectures, loc. ext., p. 53.