INFECTIOUS mononucleosis, or glandular fever, was first described in 1889 by Pfeiffer.1 The earliest report on the subject in this country was that by West2 in 1896. The hematologic aspects of the process were extensively studied during the first three decades of this century and were crystallized by the work of Downey and McKinlay3 in 1923. In 1932, Paul and Bunnell4 observed that the serum of patients with infectious mononucleosis agglutinated the erythrocytes of sheep in concentrations above a normal titer. Since then there have been numerous reports on the disease, outstanding of which is the classic review by Bernstein. . . .