He was born in Bridgeport, Connecticut on February 15, 1866, the son of Prof. William Thompson Lusk of Long Island College of Medicine and his wife, Mary Hartwell Chittenden.

[1] His maternal grandfather was U.S. Representative Simeon B. Chittenden, and his sister Anna Hartwell Lusk, was a member of Mrs. Astor's "Four Hundred" during the Gilded Age.

He did further postgraduate studies in Germany under Professor Carl Voit at the University of Munich gaining a doctorate (Ph.D.) in 1891.

[6] In 1899 (largely due to his father's Scottish roots), he was elected a Fellow of the Royal Society of Edinburgh.

He was elected a member of the United States National Academy of Sciences in 1915 and the American Philosophical Society in 1924.