More than a million young Catholics learned the hard way about a venerable Catholic tradition: "spiritual Communion" or the "Communion of desire." After a wild storm August 20 at World Youth Day in Madrid left six people injured -- including two with broken legs -- Spanish police collapsed the tents where most of the unconsecrated hosts for the next morning's Mass were being kept. Without the hosts in the tents, organizers had 5,000 ciboriums holding 200 hosts each; they were consecrated by the pope at Mass Aug. 21 and distributed to pilgrims in the section closest to the altar. Distributing Communion to just 100,000 people wasn't a decision anyone took lightly, and apparently there were long discussions with World Youth Day organizers and Vatican officials trying to find a solution. In the end, it just wasn't possible logistically to locate another 1.5 million hosts. A couple of hours before the Mass, organizers announced that most of the people present would not be able to receive; they asked the pilgrims to offer up that sacrifice for the pope's intentions and told them they could receive Communion later in the day at any church in Madrid. The decision to cancel Communion for most Mass participants was reached "with the greatest pain," Yago de la Cierva, director of World Youth Day Madrid, told reporters. Whenever there is a huge crowd for a Mass, whether in St. Peter's Square or at a World Youth Day, there always are some people unable to get to the Communion distribution point in time to receive. But in Madrid, de la Cierva said, "almost everyone" was among those not receiving. Obviously, receiving Communion is the way to participate most fully in the Mass, but it's not always possible for everyone to receive at every Mass, nor do many Catholics in the world even have regular access to Mass. The idea of "spiritual Communion" -- inviting Jesus into one's heart and soul when receiving the actual sacrament isn't possible -- is part of Catholic tradition. In the 1700s, St. Alphonsus Liguori wrote a special prayer for spiritual communion: "My Jesus, I believe you are really here in the Blessed Sacrament. I love you more than anything in the world, and I hunger to receive you. But since I cannot receive Communion at this moment, feed my soul at least spiritually. I unite myself to you now as I do when I actually receive you." Jesuit Father Federico Lombardi, Vatican spokesman, said it would be a huge mistake to believe the Mass had no value for those who were unable to receive Communion. "Communion is always an extraordinary gift, and one must be in awe of being able to receive it," he said. "It is not something one can presume to have an absolute right to as if he'd bought a ticket for it by going to Mass. Someone who thinks that hasn't understood who is in the consecrated host and what the Mass is," the spokesman said. The eucharistic adoration and benediction at the vigil in Madrid underlined that point, he said. Jesus is present in the Eucharist, which is why it is adored and why Catholics spend time in its presence, even outside of Mass. The "eucharistic fasting" many of the young pilgrims in Madrid were forced to endure could also help them be in spiritual solidarity with other people who find themselves desiring the Eucharist, but unable to receive it, he said. "I'm thinking of Catholics deprived of priests in many parts of the world for many reasons," he said, but there also are those "who would like to celebrate the Lord's Supper with other Christians, but don't have intercommunion out of respect for the norms of the church. Isn't it meaningful in these situations to know we can unite ourselves with Christ through love and desire?" In an era when people are encouraged to receive the sacrament frequently, they don't hear the term "spiritual Communion" very often, but it is still mentioned in church documents. The Vatican's preparatory document for the 2012 International Eucharistic Congress in Dublin said those who cannot receive the Eucharist can have spiritual Communion, declaring their desire to receiving the Eucharist and uniting "their suffering of that moment with the sacrifice of Jesus Christ." The working document for the Synod of Bishops on the Eucharist in 2005 addressed the idea of offering up the sacrifice of being unable to receive Communion. It said: "Spiritual Communion, for example, is always possible for elderly persons and the sick who cannot go to church. In manifesting their love for the Eucharist, they participate in the communion of saints with great spiritual benefit for themselves and the church. By offering their sufferings to God, the church is enriched." In "Sacramentum Caritatis," the document he issued in 2007 reflecting on the synod, Pope Benedict cautioned people against thinking they had "a right or even an obligation" to receive the Eucharist every time they went to Mass. "Even in cases where it is not possible to receive sacramental Communion, participation at Mass remains necessary, important, meaningful and fruitful. In such circumstances it is beneficial to cultivate a desire for full union with Christ through the practice of spiritual communion," Pope Benedict wrote.