John_Alexander_MacWilliam--John_James_Richard_Macleod

John Alexander MacWilliam (31 July 1857 – 13 January 1937), a physiologist at the University of Aberdeen in the late nineteenth and early twentieth centuries, was a pioneer in the field of cardiac electrophysiology. He spent many years studying ventricular fibrillation, and was the first person to propose that ventricular fibrillation was the most common cause of sudden death - and that fibrillation could be terminated (and life potentially saved) by a series of induction shocks to the heart. He was the first to accurately describe the condition of arrhythmia (irregular heartbeat), and he suggested transthoracic pacing to treat transient asystole (cardiac arrest).
Although his work was recognised within his lifetime, it was not until many decades later that it laid the foundations for developments in the understanding and treatment of life-threatening heart conditions, such as in the artificial cardiac pacemaker.
MacWilliam was appointed Regius Professor of the Institutes of Medicine (later Physiology) at the University of Aberdeen at the age of 29 in 1886, and remained in that post for 41 years until his retirement in 1927.