Mabel FitzGerald has been all but forgotten in the study of human acclimatisation to high altitude. Her great scientific accomplishment was to demonstrate, over the long term, that it is oxygen, and not carbon dioxide, that determines how hard we breathe and sets the haemoglobin concentration in our blood. This she did by travelling around Colorado, USA in 1911, as part of the University of Oxford Laboratory of Physiology’s landmark Pike’s Peak Expedition, making detailed physiological measurements of the populations living at different altitudes throughout the state.

Mabel FitzGerald had a middle-class upbringing, but her life abruptly changed in 1895 when both her parents died. She came to live in Oxford with her four sisters in 1896 in a house in Crick Road, just north of the University Parks, next door to John Scott Haldane, then a Demonstrator in the Laboratory of Physiology. FitzGerald was fascinated by physiology and her local doctor recommended a career in the medical sciences. The University permitted her to attend Physiology classes informally under Gustav Mann from 1896-1899. She gained top marks in the examinations, but these could not count towards a degree because women could not be officially enrolled. In 1897, FitzGerald started her first research position with Francis Gotch and Gustav Mann at the Laboratory of Physiology, where she developed an expertise in histology. Her histological work on tissue response at vaccination sites was included in a manuscript published by Mann in 1899.

After her studies, FitzGerald became the Laboratory Technician to John Scott Haldane in the Laboratory of Physiology and by 1905 was named on one of his papers. She came to the attention of Sir William Osler, Regius Professor of Medicine at the time, who recommended her for a Rockerfeller research grant, which she won in 1907. This grant took her to the USA where she conducted pioneering research. In 1911, she returned to Oxford and became part of an expedition to Pike’s Peak, Colorado, led by Haldane and C. G Douglas, to examine the effects of low atmospheric pressure on respiration. Their discoveries revolutionised current ideas about respiration.

She was “rediscovered” by accident in the 1960s, still living in her house in Crick Road. With the help of the then Regius Professor of Medicine, Sir Richard Doll, the University of Oxford finally bestowed an honorary Master of Arts degree on her in 1972 – the first centenarian to receive one. Sir Richard wrote that her example first convinced Oxford “that women can do as well as men”. On bestowing the degree, the then Vice Chancellor, Alan Bullock, acknowledged that it had come three-quarters of a century too late.

Based on her pioneering work in Colorado, Mabel FitzGerald became only the second female member of the American Physiological Society in 1913, but it was not until 1973 that she was made an honorary member of the British Physiological Society. She was then the American Physiological Society’s oldest living member.