Why are you an atheist?

[Oldandeasilyconfused]

But the communion wafers are supposed to be his body, aren't they? Maybe his trick was to just get a bread knife and go to work on his own arm?

You're into can-of-worm territory there mate.The nature of the host (wafer)was a significant issue during the reformation. At least within the clergy and other 1% or so of people in Europe who could read at the time.

The argument was about TRANSUBSTANSIATION, Viz the Catholics claimed,(and still do)that at the moment of Consecration during the Mass,the bread and wine LITERALLY becomes the body and blood Christ in all but appearance,texture, smell and taste.(No really, I'm not making this up)

Unsurprisingly,Martin Luther took issue with this claim,stating Christ is present only IN ESSENCE,not literally. With this crucial disagreement,each side began slaughtering heretics on the other side as often as possible.

From Wiki:

In Roman Catholic theology, transubstantiation (in Latin, transsubstantiatio, in Greek μετουσίωσις (metousiosis)) means the change of the substance of bread and wine into the Body and Blood of Christ occurring in the Eucharist while all that is accessible to the senses remains as before.[1][2]

http://en.wikipedia.org/wiki/Transubstantiation