When did the Church teach that each species contains both Christ's body and blood?

Transubstantiation was officially defined in 1215 at the Fourth Lateran Council. But the Church has always held that Christ is present whole and entire in each species and in each of their parts (CCC 1377).

The Council of Trent (1551) declared that, because Christ said that what he offered under the species of bread was truly his body, the Church has always been convinced, and now declares again, that by the consecration the whole substance of the bread is changed into the substance of Christ's body and the whole substance of the wine into the substance of his blood, a change fittingly called transubstantiation (Denzinger-Schönmetzer 1642).

The Catechism adds that Christ's Eucharistic presence begins at the consecration and lasts as long as the species subsist, and that he is present whole and entire in each species and each part, so that breaking the bread does not divide Christ (CCC 1377).