Born in Ireland on Earth, Corrigan was one of the first off-world scientists to come to the Academy. He was teamed with the Vulcan healer Sorel for the first time in the late 2220s; their combined efforts resulted in the conception and birth of Spock, the first Vulcan-human hybrid. Their professional (and personal) association would last for well over four decades after that - by 2267, they were renowned as the best medical team on Vulcan. Corrigan would be the primary physician for many of the humans living on Vulcan, including Amanda Grayson, wife of Sarek and mother of Spock.
When he was affected by a condition that caused rapid physical aging, Corrigan's mind remained clear enough to allow him and Sorel to develop their methodology and find a way to save his life via a stasis-regeneration treatment. The regeneration not only arrested the condition, but also had the unexpected effect of reducing his physical age (Corrigan, by that time in his early seventies, came out of it looking like he was in his mid-thirties). This process would also be used for Sorel's wife, T'Zan, injured in an accident in the neurosciences lab, a crewman of the USS Enterprise critically injured in battle, and Amanda Grayson, suffering from degenerative xenosis.
When T'Zan died as a result of what appeared to be equipment failure, Corrigan – though at first blaming himself for trying "untested treatments" on his patients – aided in the investigation, led by James T. Kirk, into what exactly happened. Kirk originally theorized that the intent was to discredit Sorel and Corrigan's work and break up their partnership. During the height of the incident, Corrigan bonded with Sorel's daughter T'Mir, finding that they had shared a mutual attraction for one another; this led to an attack on Corrigan by a Vulcan radical named Sendet, leading the others to believe that he had been behind the "equipment failures" (in reality, sabotage) that had killed T'Zan and later the Enterprise crewman. Upon Sendet being cleared of that crime (but discovering several unrelated ones in the process) and the discovery of the real killer - a deranged assistant of Sarek who attempted to kill Amanda so she could marry him - Corrigan and Sorel continued their work at the Academy with the successful treatment of Amanda's condition. (TOS novel: The Vulcan Academy Murders)
Sometime later, a plague broke out on the planet Nisus, and Corrigan – accompanied by his wife T'Mir – joined Sorel onboard the Enterprise to lend their aid. They were again teamed with the Enterprise medical officer, Dr. Leonard McCoy, with whom they had worked during the Vulcan Academy incident. This was the first time that Sorel and Corrigan as a team (and Sorel personally) had left Vulcan. (TOS novel: The IDIC Epidemic)