It has become a ritual for medical writers to begin a textbook, and often, articles in journals on infectious mononucleosis by stating the disease was first described by Pfeiffer under the name of "Druesenfieber" (glandular fever) in 1889. Wising stated that Filatow, in 1885, described what probably was mononucleosis, but "the honor of distinguishing infectious mononucleosis as a characteristic entity" should be ascribed to Pfeiffer.
Now, this is very odd because mononucleosis, of course, means predominance of mononuclear leukocytes, but neither Filatow nor Pfeiffer knew of differential blood counts. Examination of stained blood smears had not yet been introduced into