there is no wine in a communion service as bread and wine are consecrated only during Mass. the sacred hosts distributed in a communion service have been consecrated at an earlier Mass and reserved in the tabernacle. During Mass the Precious Blood must be consumed by the priest if there is any left after communion. Hosts are reserved in the tabernacle for the sick, for those in danger of death, and for communion services on days there is no priest to say Mass.
if it is a situation, mass or communion service, where the sacred species cannot or are not going to be reserved in the tabernacle, they are reverently consumed after communion is over. (for example mass while camping, the priest eats the extra hosts after everyone recieves.
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