William George MacCallum

William George MacCallum, born on April eighteenth, eighteen seventy-four, in Dunnville, Canada, was a distinguished Canadian-American physician and pathologist of Scottish descent. His early education took place at the University of Toronto, where he earned a Bachelor of Arts degree in eighteen ninety-four. Although initially drawn to a career in academia focused on Greek studies, his father's influence guided him toward the field of medicine.

In eighteen ninety-seven, MacCallum joined the Johns Hopkins Medical School as part of its inaugural medical class, graduating as one of its first alumni. His career at the institution flourished as he took on various roles, including assistant resident of pathology in the same year, resident pathologist in nineteen oh one, and eventually ascending to full Professor by nineteen oh eight. Between nineteen oh nine and nineteen seventeen, he held a dual appointment as Professor of Pathology at both Columbia University and the NewYork–Presbyterian Hospital, before returning to Johns Hopkins University to chair the Department of Pathology from nineteen seventeen until nineteen forty-three.

MacCallum's contributions to pathology are notable, particularly his discovery in eighteen ninety-seven of two forms of the malarial parasite in birds, which are now recognized as male and female gametes. In eighteen ninety-nine, he collaborated with T.W. Hastings to identify a new species of pathogenic Gram-positive bacteria, Micrococcus zymogenes. His pioneering work also included elucidating the distinct functions of the thyroid and parathyroid glands in nineteen oh five, and he was instrumental in understanding the role of calcium in muscle contraction.

In nineteen oh nine, he clarified that gastric tetany was not related to parathyroid functions but rather due to a blockage in the stomach-intestine connection. His authoritative textbook, A Textbook of Pathology, has seen multiple editions and remains in print today. Additionally, the MacCallum-Goodpasture stain, a histochemical technique for Gram-negative bacteria, bears his name alongside co-discoverer Ernest William Goodpasture, and the MacCallum plaque, a condition associated with rheumatic heart disease, is also named in his honor.