Glass ampullae: devotion to the blood of the martyrs

The glass jars often placed inside small niches on the outer sides of the arcosolia were “blood ampullae”, very common in the catacomb of San Giovanni.
The ampullae were used by the first Christians to hold the blood of the martyrs.
The jars were kept in the tomb of the martyr to bear witness to their glorious death by the faith of Christ.