The diagnosis of influenza, even in times of epidemic, is not always easy, and by no means certain, in the absence of bacteriologic evidence. Catarrhal symptoms referable to the respiratory and digestive tracts, articular and muscular pains, elevation of temperature and other manifestations supposed to be more or less distinctive of influenza are not rare, singly or collectively, as a result of a variety of causes, particularly during the cold season. It would, therefore, seem that the demonstration of influenza-bacilli in the discharges or the blood is, at the present time, as important a factor in the diagnosis of influenza as is the demonstration of tubercle bacilli or of diphtheria bacilli in the diagnosis of tuberculosis or diphtheria.
The following method for staining the sputum for various bacteria is described by Dr. Wm. H. Smith,1 in whose hands it has proved most serviceable. The dried and fixed cover-glass preparation