The sound of a little bell rings out three times in one paragraph of Proteus as Stephen imagines priests in various churches and chapels performing their sacred rites: "elevating" the consecrated Host (the priest lifts the wafer toward the heavens and then kneels before the altar), "locking it into a pyx" (a receptacle for the holy bread), and "taking housel all to his own cheek" (housel is the act of administering or receiving the Host, so the priest is taking communion). At each of these moments Stephen imagines hearing the sound of the small "sacring bell" or "sanctus bell" that marks important moments in the Catholic liturgy.
All three rituals date to the time, notably the 12th century,
when Catholic theologians formulated their doctrine of transubstantiation,
according to which the bread held by the priest becomes
literally changed into the body of Christ. The now holy bread
had to be protected from loss, theft, and degradation, so a
small, precious, and lockable box called a "pyx"
was installed in churches. Normally only priests were allowed
to "take housel": in 1215 the fifth Lateran Council
specified that laypersons should be able to receive communion
at least once a year (usually Easter). Since the congregation
could not participate in the rite themselves, elaborate
rituals were devised to let them see and hear the moment of
consecration. The priest, facing away from them toward the
altar, would "elevate" the bread as high as he could
reach so they could see it over his head, while bells rang and
candles burned and incense smoked. In the days before the
Super Bowl and the World Cup it was apparently great spectator
sport: some people would go from church to church to see the
miracle performed multiple times in one day.
Stephen's imagination is running along such lines when he thinks of bells sounding in multiple places at the same time. To him, this fact suggests how the medieval theologian William of Occam might have conceived his theory of a single body of Christ incarnated simultaneously in different pieces of bread. The argument works by analogy with the pairing of musical notes or spoken vowels: "Bringing his host down and kneeling he heard twine with his second bell the first bell in the transept (he is lifting his) and, rising, heard (now I am lifting) their two bells (he is kneeling) twang in diphthong." When priestly celebrants in different parts of a church lift their wafers up toward God and kneel before their separate altars, sanctus bells "twine" with one another in the air, or "twang in diphthong." Just so, multiple wafers make up a single body of Christ.
The "sound of the sacring bell" appears also in Cyclops, to introduce an absurdly huge procession of churchmen and churchwomen.