THE MORPHOLOGY OF THE INFLUENZA BACILLUS

Pfeiffer1described a "true influenza" bacillus and a "pseudo-influenza bacillus." He was unable to distinguish these organisms in direct smears of exudates, where they both appeared as small bacilli with rounded ends. Culturally they were identical. He based his distinction on the fact that smears from cultures of the true influenza bacillus showed small bacilli with few longer forms, while smears made from cultures of the pseudo-influenza bacillus showed long, threadlike organisms. The pseudo-influenza bacillus was isolated by Pfeiffer from three cases of bronchopneumonia. In bacteriologic examinations of the sputum, blood and lungs during the present epidemic of influenza, both forms of the influenza bacillus have been encountered. In some cases aerobic plates of the sputum have yielded practically pure cultures of the small gramnegative bacillus contaminated only by rare colonies of staphylococcus. Sputum from other cases has yielded equally pure cultures of the long, threadlike organism designated by