The Institution of the Eucharist

Brothers and sisters:
I received from the Lord what I also handed on to you,
that the Lord Jesus, on the night he was handed over,
took bread, and, after he had given thanks,
broke it and said, "This is my body that is for you.
Do this in remembrance of me."
In the same way also the cup, after supper, saying,
"This cup is the new covenant in my blood.
Do this, as often as you drink it, in remembrance of me."
For as often as you eat this bread and drink the cup,
you proclaim the death of the Lord until he comes.

1 Cor 11:23-26

I have known people who suffer an adverse reaction when exposed to depictions of the Last Supper like those above. "The bread didn't look like a host!" they exclaim.

They miss the point. These pictures aren't trying to faithfully reproduce a historical scene. They are nonetheless depicting a historical reality. When the priest says the words of consecration over the hosts at mass, they become no less the body of Christ than when Jesus himself said those words in the Upper Room. When we attend Mass, we place ourselves at the Last Supper. The priest acts in persona Christi, and what was bread and wine becomes the body and blood of our Lord. And, when Christ blessed the bread at the Last Supper, he was instituting the Eucharist. The host we receive is, in substance, the same as the bread that He gave to his apostles.