[2][3] She was the seventh of nine children, one of her brothers being professor Simon Henry Gage of Cornell University.

She passed one year studying physiology, zoology, and anatomy,[1] in the scientific laboratories of Cornell University,[5] in 1884, her medical preceptor being Burt Green Wilder, M. D. Day attended two courses of medical lectures in the Department of Medicine and Surgery of the University of Michigan, Ann Arbor, Michigan, and was graduated in 1888.

[1] Day commenced the practice of medicine in October, 1888, at Wichita, Kansas, which she continued for fifteen months, and then accepted a position as resident physician at the hospital of the Michigan State Public School for Homeless Children, for ten months.

[5] In 1889,[6] after doing original research for a year and a half, Day published several papers on Locoweed, including two articles on Locoweed in the New York Medical Journal,[1] from which the definition of “Loco Disease” was made up in Frank Pierce Foster's New Medical Dictionary.

This article was written after extensive observation of the suffering caused to livestock from eating the locoweed and after much experimental work upon animals.

[7][3] Day made her home in Kingston,[7] where she was a member of St. John‘s Episcopal Church.