We see a sign of the changes wrought by Vatican II in the title of today's feast. We old-timers remember when it was just called "Corpus Christi:" the Body of Christ. The Blood of Christ got short shrift. For good reason; before the Vatican II reforms the laity were forbidden to receive from the cup. Even today the cup minister often has little to do during celebrations of the Lord's Supper. Many priests look for any excuse to avoid offering the cup to the entire community. Rarely do we hear a homily encouraging people to receive both species. After all, we learned in those pre-council days that if you receive Jesus' body, the blood's automatically there. For many, it's simply a matter of extra credit - something they don't really need to get into heaven. Besides, there're all those germs!
It's clear from our Christian Scriptures that our ancestors in the faith would have been appalled at the excuses we use for refusing the cup. In the earliest mention of the Lord's Supper - I Corinthians 11 - Jesus tells his followers, "This cup is the new covenant in my blood. Drink it and remember me."
These words take us back to our first reading. Note what Moses says about the blood sprinkled on the people at the foot of Mt. Sinai. "This is the blood of the covenant that the Lord has made with you in accordance with all these words of his."
Covenants normally include signs that the participants have entered into those agreements. Many workers and employers have copies of signed contracts outlining each party's responsibilities and benefits. Most married couples wear wedding rings to show they're committed to one another.
The outward sign the Israelites had entered the Sinai covenant with Yahweh was the blood on their clothes and skin. In a parallel way, the outward sign Christians have joined Jesus in living up to the covenant he made with his Father is their reception of his blood from the Eucharistic cup.
Marcan scholars frequently point out an overlooked part of his Last Supper pericope. "He (Jesus) took a cup, gave thanks, and gave it to them and they all drank from it." In Mark's narrative, the last meal Jesus eats with his followers is a Passover Supper. In such ritual meals, each participant has her or his own cup of wine sitting on the table in front of them. Yet, at a very important point in Mark's account, Jesus tells his disciples not to drink from those cups. He passes his own cup around the table. By drinking from Jesus' personal cup, they're demonstrating their determination to carry on his ministry after his death. I can't imagine what would have happened had any of that night's supper guests refused to drink from his cup because of germs or because they bought into a theological opinion that the body under the form of the bread they'd just received already contained Jesus' blood. I suspect the about-to-die Jesus would have confronted their refusal with some form of "It's my way or the highway!"
Nothing is wrong with surfacing the deep Jewish sacrificial significance of Jesus' shedding his blood for us. The author of Hebrews does so in today's second reading. But long before Christian authors began reflecting on that deeper, esoteric significance they had to deal with the evident implications of actually drinking his blood. Some scholars contend that one reason we receive Jesus' body first is to give us the strength to then step up and receive from his cup.
We Catholics obviously have a long way to go before we understand and practice signs which our ancestors in the faith took for granted.