Not all Christian's believe the cracker is the actual body of christ. Many recognize (rightly so) that the cracker is a symbol.
Please do not lump all Christian beliefs into one general idea, when there are many different denominations (versions) of the religion.
As far as speaking in tongue's goes, it was originally the idea that God would give the person the ability to talk to someone of a different language background. For example, a guy that speaks only English would be able to speak Mandarin Chinese fluently, without ever having studied the language. Modern speaking in tongue's is just a bastardization of that, and there are even Christian's who recognize that many people that practice it, are doing it wrong.