The meaning of the punishment of the suicides is evident: In Hell, those who on Earth deprived themselves of their bodies are deprived of human form. At the Last Judgment the suicides will rise, like all the other souls, to claim their bodies, but they will never wear them. Their bodies will remain suspended on the trees that enclose the spirits of their owners.
One of the greatest changes brought on by the advent of Christianity is the change that took place in judging the suicide. In classical times, when a person could no longer live in freedom, or heroically, it was considered a stoic virtue to die by one's own hand. The last great act that a person could perform was to take his or her own life, which was the last free choice that person could make.
With the coming of Christianity, however, Jesus preached the concept that a man is free inwardly, and no amount of imprisonment or disgrace could destroy one's spiritual self. Thus, where the suicide was a virtue in the ancient days, for the Christian, it became one of the cardinal sins; murdering the body that God gave unto one.
Dante is naturally very confused when he arrives at the wood of suicides and hears human sounds but sees no human forms. Consequently, Virgil has to do something that seems extremely cruel. He has Dante pick off a branch from one of the trees, which causes the tree to bleed. Dante has previously shown that he is a person of infinite pity; therefore, the words of the tree evoke an unexpected response — surprise and sympathy.
