Because doubt has entered the hearts of the clergy and the laity on the Mystery of Transubstantiation, the miracle that transforms the bread and wine into the Body, Blood, Soul, and Divinity of Our Lord, Miracles have occurred to prove that the Real Presence of the Sacred Species is true according to the teaching of the Catholic Church. The Host and the Wine are transformed into real flesh and blood.
However, most of all, it is to address and to demonstrate to those who scoff, deride and ridicule
St. John's Gosple (Chapter 6), and disbelieve in the words spoken by Jesus that to have eternal life, one must
eat His Flesh and drink His Blood. He spoke literally but many walk away because this teaching was hard on their
ears -- how can the Son of Man speak of "cannibalism"? Jesus nevertheless did not call them back nor
to explain that He was speaking in parables, and what He said meant it only symbolically.
Lanciano, Italy -- 8th Century
Blanot, France -- March 31, 1331
Amsterdam, Holland 1345
Siena, Italy -- 1730 AD
St. Anthony of Padua (http://www.catholiceducation.org/articles/religion/re0552.html)