Macallum was born in
Belmont,
Canada West, the son of a Scottish immigrant and one of twelve children. He grew up speaking
Gaelic at home, learning English at school. He attended high school in
London, Ontario and became a teacher after graduation. After saving money for several years he entered the
University of Toronto. There he was influenced by biology professor
Ramsay Wright; at 22 he earned a
Bachelor of Arts (B.A.) degree and was awarded the medal in natural science. Over the next several years, he taught high school in
Cornwall, Ontario and continued scientific work under Wright's direction. In 1883, he became a lecturer in biology at the University of Toronto and started work on a medical degree, studying both with Wright and with
H. Newell Martin of
Johns Hopkins University. In 1888 he earned a Ph.D. from Johns Hopkins, and two years later completed a medical degree from the University of Toronto; he then became the first chair of
physiology at Toronto. In his first years as physiology chair at the University of Toronto, Macallum and several other biologists trained by Wright (
anatomy chair
James McMurrich and pathology professor
J. J. Mackenzie) fought to replace the Toronto medical school's traditional medical education with a curriculum based on biological science. They had largely succeeded in this by 1908, when Macallum became Chair of Biochemistry, a newly created position. In 1917, he left academia to organize the
National Research Council. In 1920 he returned to chair the new Department of Biochemistry at
McGill University, where he stayed until retirement in 1928. Macallum was an elected International Honorary Member of the
American Academy of Arts and Sciences and an International Member of the
American Philosophical Society. ==Scientific work==