It is interesting to note how widely divergent have been the experiences of clinicians concerning the usefulness of direct smears in diphtheria, and singularly so to compare the statements in textbooks on bacteriology and pathology to those appearing in books on pediatrics and medicine, for although the former are in accord that a smear suitably secured and stained will, in a large portion of cases, perhaps in half or more, furnish good evidence of the presence of diphtheria, such a belief, although to be found, does not commonly appear among methods deemed suitable for the physician.
The inherent difficulty, it seems, lies in the fact that grown on living tissues, the diphtheria bacillus appears in a great variety of forms, and that these take stains indifferently well and are, therefore, not so readily distinguishable as when obtained in culture. Everyone who has attempted to find them knows that this is
BLEYER A. CONCERNING DIRECT SMEARS IN DIPHTHERIA. Am J Dis Child. 1920;20(5):445-460. doi:10.1001/archpedi.1920.01910290107006