MacCallum, William George
William George MacCallum, pathologist (b at Dunnville, Ont 18 April 1874; d at Baltimore, Md 3 Feb 1944). After graduating in 1894 from the University of Toronto, he entered Johns Hopkins Medical School and graduated with an MD in 1897. He took up the study of pathology after a year as intern. This study took him first to Columbia University and finally in 1917 to professor of pathology at Johns Hopkins. Besides writing a textbook of pathology which went through several editions, he made discoveries on the life cycle of the malarial parasite and the physiology of the parathyroid gland, and studied valvular lesions of the heart and the pathology of influenza. In 1919 he discovered the stain, known as MacCallum's stain, which is used to render influenza bacilli visible under a microscope.