Council of Trent: Session XXI, Communion, Chapter III

CHAPTER III. That Christ whole and entire, and a true Sacrament are received under either species.

It moreover declares, that although, as hath been already said, our Redeemer, in that last supper, instituted, and delivered to the apostles, this sacrament in two species, yet is to be acknowledged, that Christ whole and entire and a true sacrament are received under either species alone; and that therefore, as regards the fruit thereof, they, who receive one species alone, are not defrauded of any grace necessary to salvation.

Translation: J. Waterworth, The Canons and Decrees of the Council of Trent (1848), Hanover Historical Texts Project transcription (1995).