The winter of 1889-90 is indelibly engraved on the history of great epidemics. An influenza epidemic greater than any before arose in the far East, spread like a hurricane through Europe, and thence over the greater part of the earth. Four decads after the last European pandemics (1847-48) the medical profession of our day found itself confronted by a new disease, which up to that time had been known to them only in the history of medicine. The interest which the affection everywhere elicited, the competition which it kindled in all civilized lands to apply to the new disease the progress and the acquisitions of modern medicine, advanced our knowledge of influenza in every direction.
Men became absorbed anew in the history of influenza and extended its study to a diligent examination of the oldest sources, as is shown in the excellent monographs of Ruhemann, Ripperger, and Kusnezorn-Herrmann. The classic essays of Most (1820), Schmeich (1836), Gluge (1837), Canstatt (1847), A. Hirsch (1860-81), Biermer (1865), Haeser (1876), Zuizer (1886), the important works of Peacock (1847) and T. Thompson (1852) in England, Saillant (1870) and Ozanam (1835) in France, Zeriani (1804) in Italy, received anew their well merited recognition. The most important result of these historic researches was the proof that the last pandemic, both in its epidemiologic character and also in its clinical picture, symptoms, and protean variations, was identical with the influenza of former decads and centuries.
Epidemiologic investigation is much indebted for its progress to the accuracy of modern statistics, to the high development of medical journalism, and to the powers that have been universally brought to bear toward achieving collective investigations and scientific researches.
Among the important works of recent times the following may be mentioned: The German Collective Investigation Report, edited by A.
Gey der and S. Guttmann; the exhaustive reports on the epidemic of influenza (1889-92) of Parsons; the report of the French Academy by Proust-Brouardel, and the army report of Kelsch and Antony; the account of influenza in Russia reported by Teissier; the Belgian " Enquete sur l'epidemie de grippe"; the Dutch report of Wertheim Solomonson and de Rooj; the Danish report by Carlsen; the Swedish, by CI. Linroth; the Egyptian by Engel-Bey, as well as reports of collective investigations from Australia, Massachusetts, Riga, Cologne, and Danzig.
Worthy of particular mention are the reports of the Imperial Board of Health in Berlin, containing the comprehensive compilation of the statistics of the German Empire regarding the influenza epidemic of 1889-90, by P. Friederich, and the epidemic of 1891-92 by Wutzdorff; the official report on influenza in Switzerland, 1889-94, by F. Schmid; and, finally, the report published by the Prussian War Office on " Die Grippe-Epidemie im deutschen Heere, 1889-90," and the "Deutsche Marinebericht," compiled by Elste.
The most important advance in epidemiology was the universal acceptation of the doctrine of the contagious nature of influenza, of its transmission from person to person, and its dissemination through human intercourse. These views, although supported by the older authors, were again and again disputed by the majority of physicians even up to and at the beginning of the latest pandemic. There is now an overwhelming amount of material, collected from every scource, placing this doctrine on a firm foundation.
One of the oldest supporters of the view regarding the contagion of influenza was Ch. Calenus (Greifswald), who in 1579 wrote: " Contagiosum dico Morbum, quia etsi quidem ab occulta quandem coeli influentia principaliter eum profisci hauo dubium est . . . eo in loco quo jam grassabatur inter homines citius eos invadebat, qu cum affectis frequenter conversabantur, quam eos, qui a consuetudine affectorum studiose abstinebant." But the real birthplace of the doctrine of contagion is England, where it was formulated upon facts, which will be discussed in detail later, by Haygarth, Hamilton (" cause not in the air, but in a specific contagion"), Gray, Hull, Duggard, Bardsley, and others, during the epidemics of 1775-1803. In addition we may mention among the supporters of the contagion theory Simonin, Lombard, Petit de Corbeil (1837), Blanc (1860), and Bertholle (1876). To Ch. Baumler (1890) is due the credit of disseminating the law of contagion through Germany.
The guiding science in the etiology of the acute infectious diseases, namely, bacteriology, solved the difficult problem of finding the specific cause of this disease only after repeated attempts and failures. Should the Bacillus influenzae, discovered by R. Pfeiffer in 1892, continue to maintain in future pandemics its place as the exclusive cause of the disease, as may certainly be expected, its discovery may be considered as the most important achievement of our latest influenza pandemic. It remained for clinical and anatomic investigation to complete the structure founded by our ancestors, and to arrange it in accordance with the progress of science. The pandemic of 1889 was the first to occur in the period of specialism of modern medicine. For this reason many symptoms, complications, and sequelae which had in former times been overlooked received now for the first time thorough investigation and recognition. In how high a degree the science of medicine performed its task, a glance at the almost boundless literature of influenza will show. The progress of recent years in epidemiology, etiology, and clinical medicine, already mentioned, makes it self evident that we must employ the perfected experience of our latest pandemics as the foundation of our treatise. Nevertheless, we cannot entirely omit a retrospect to the history of former epidemics.