They’ve become an optional memorial in the current Roman Calendar, displaced from their traditional feast day on Sept. 27 because the Church decided that St. Vincent de Paul is more significant to Catholics of our times. But Sts. Cosmas and Damian are always mentioned in the First Eucharistic Prayer and, since the Roman Canon was the Eucharistic Prayer for centuries, the fact these two brothers are included every time it is prayed suggests we learn something about them.