1. Transubstantiation is described by the Council of Trent as the change of the whole substance of bread (totius substantiae panis) into the body of Christ, and of the whole substance of wine (totius substantiae vini) into the blood of Christ, the species of bread and wine remaining unchanged (Session XIII, can. 2; D 884). This notion of transubstantiation is coloured by the branch of philosophy known as cosmology and is the result of a development which was not always consistent. Though the element of change (metabolismus) had been expressly stressed by St. Ambrose (see J. Geise…