During his childhood he became interested in the medical profession, and (although records from the time are vague and incomplete) is believed to have graduated from the College of Physicians and Surgeons at Columbia University in 1845.
Later, while studying under a phrenologist, he had the opportunity to examine the heads of a number of Egyptian mummies, and concluded that embalming could be achieved without the use of hazardous compounds.
Immediately prior to the American Civil War, Holmes experimented with arterial embalming based on the earlier work of Jean-Nicolas Gannal of Paris.
[3] Abraham Lincoln eventually sanctioned the treatment for all fallen soldiers and officers, and in four years Holmes embalmed several thousand bodies.
Thomas Holmes—later known as the “Father of Modern Embalming—offered his services to Col. Elmer Ephraim Ellsworth's family, and the Colonel's preserved body was taken to the White House, where it lay in state for several days.