The Miracle of the Mass. "Bread was handled on the altar before the sacramental words. At the consecration, from bread there became the flesh of Christ. But how could it belong to bread to be the body …More
The Miracle of the Mass.

"Bread was handled on the altar before the sacramental words. At the consecration, from bread there became the flesh of Christ. But how could it belong to bread to be the body of Christ? The consecration happens, therefore, by which words and whose pronouncement?—Those of the Lord Jesus. All the rest that is said [in Mass] is praise offered to God, or petitions made for the people, for kings, and for others. But when the sacrament is effected, the priest does not use his own words, but the words of Christ. Therefore the pronouncement of Christ effects this sacrament" – from the Decretals of Gratian. Detail of the Consecration of the Host from the 14th-century 'Altar of the Poor Clares' in Cologne Cathedral.

Source: Lawrence OP on Flickr