He taught at his alma mater, Harvard University. He was instructor in pathological anatomy in 1870–1873, assistant professor in 1873–1878, and professor from 1878 to 1908. In the latter year, he became professor emeritus.
In 1886, he published "Perforating Inflammation of the Vermiform Appendix; With Special Reference to Its Early Diagnosis and Treatment". This groundbreaking paper provided analysis of 466 cases of abdominal disorders that had previously been variously diagnosed and showed that they all involved a diseased appendix. He also introduced the term appendicitis. Dozens of names had previously been used for what had been thought to be a variety of diseases.
This article incorporates text from a publication in the public domain: The New International Encyclopedia (1st edition). Gilman, D. C. and Peck, H. T. and Colby, F. M., eds. New York: Dodd, Mead, 1905.