St. Januarius, who was Bishop of Benevento, close to Naples, during the fourth century, is the patron of blood banks.   He was persecuted and arrested while visiting imprisoned deacons and later martyred with them.  

In the Breviary it is written that "Timothy, President of Campania," ordered the persecution of Januarius, who was thrown into a fiery furnace, but that the flames would not touch him. Afterwards Januarius was exposed in the amphitheatre to wild beasts, but this failed too as the beasts left him alone. Timothy declaring that this was due to magic, sent Januarius back to prison.   Shortly thereafter, Timothy became blind and demanded that Januarius help him.   Januarius cured him, and five thousand persons were converted to Christ.   When Timothy saw this, he feared his own safety and gave the command to behead Januarius.

Januarius' blood is kept in Naples, as a relic.   It is well known that when the blood of St. Januarius, that is kept dried up in a small glass phial, is put in sight of the head of the same martyr, the blood melts and transforms itself back to liquid and bubbles in a very strange way, as though it had been freshly shed.   It is especially this miracle of the liquefaction which has given celebrity to the name of Januarius.   For more than four hundred years this liquefaction has taken place at frequent intervals.

Eighteen times in each year, on the Saturday before the first Sunday in May and the eight following days, on the feast of St. Januarius (19 Sept.) and during the octave, and on 16 December, a silver bust believed to contain the head of St. Januarius is exposed upon the altar, and the reliquary just described is brought out and held by the officiant in view of the assembly.