Complex sentence: He became full Professor in Physiology at the University of Toronto in 1950: during a leave of absence from the University, he was Chief Superintendent, the Defence Research Medical laboratories 1955-1958.
Split into simpler sentences: He became full Professor in Physiology at the University of Toronto in 1950. During a leave of absence from the University, he became Chief Superintendent at the Defence Research Medical laboratories 1955-1958.