In a Catholic mass, just before the distribution of communion to people, the priest breaks the Host in to pieces and people simultaneously acclaim: Lamb of God you take away the sins of the world, Have mercy on us.......
What is the significance of this fraction of bread (Host)? Does it have any parallel to the act of sacrifice for atonement of sins: like sacrificing of lambs in OT and then sacrifice of Jesus himself for our sins?
Also the shape of this fractioned Host is different at different times. Are there any laid down norms for this?