Who are Cosmas and Damien? Their names are mentioned in the Canon of the Mass (Eucharistic Prayer I). A church was erected on their burial place, and a famous basilica was built in their honor in Constantinople. The Church in the West celebrates their memorial on September 26. But little is known about these twin brothers who lived and died during the persecution of the Emperor Diocletian. According to legend, the twins lived in Arabia and became skilled doctors. In the East, they are venerated as the “moneyless ones” because they refused to charge a fee for their services–instead helping rich and poor alike to find comfort and healing. One story that has been told is that they successfully performed the first leg transplant: They saved the life of a deacon by the name of Justinian by amputating his diseased leg and replacing it with the leg of another man, a black man, who had died.