This altarpiece, the first known work by Sassetta, was commissioned by the "Arte della Lana", i.e. the woolmerchants' guild for the church of the Carmelite Order in Siena in 1423. It was made for the feast of Corpus Christi. It upheld the doctrine of transubstantiation according to which bread and wine is changed at the Eucharist into the actual Body and Blood of Christ.

The triptych was dissembled in 1777, and the central panel is lost, but it is possible to reconstruct its original arrangement from earlier descriptions. According to these, the central panel represented the Holy Sacrament in an ostensory adored by a number of angels around it. Above this there was the scene of the Coronation of the Virgin, and on the sides Abbot S. Anthony and S. Thomas Aquinas were depicted. Above these the scene of the Annunciation was represented in two separate pictures.

On the predella underneath the main panel, seven small panels showed the following scenes: 1-2. Two scenes from the life of S. Anthony, one of them is about his temptation (Siena, Pinacoteca); 3. Execution of an Heretic on the Bonfire (Melbourne Museum); 4. The Last Supper (Siena, Pinacoteca); 5. The Miracle of the Holy Sacrament (Barnard Castle, Bowes Museum); 6. S. Thomas Aquinas in Prayer in front of the Altar of the Virgin (Budapest, Museum of Fine Arts); 7. S. Thomas Aquinas in Prayer in front of the Crucifix (Vatican, Pinacoteca).

Further to the above mentioned ones we know eight panels from the external pillars that represented the Four Doctors of the Church: S. Jerome, Gregory, Ambrose, Augustine as well as the four patron saints of Siena: S. Ansanus, Victor, Savinus and Crescentius. Two small panels from the pinnacles with the figures of the Prophets Elias and Eliseus still exist in the Sienese Picture Gallery. Under the central panel the following inscription was visible: "Hinc opus omne Patres Stefanus construxit ad aras Senensis Johannis agens citra lapsus adultos". The interpretation of this distych is much debated.

The iconographic programme of the altar was probably composed by the Carmelite monks. That is why the two prophets, Elias and Eliseus, the "Dux et Pater" and the Pater of the Carmelites were represented on the altar, and in Carmelite habit. We can also see a few Carmelite monks in the pictures of the predella.

Preview	Picture Data	Info
	St Anthony the Hermit Tortured by the Devils 1423 Panel, 24 x 39 cm Pinacoteca Nazionale, Siena
	Death of the Heretic on the Bonfire 1423 Panel, 24,6 x 38,7 cm National Gallery of Victoria, Melbourne
	The Last Supper 1423 Panel, 24 x 38 cm Pinacoteca Nazionale, Siena
	Miracle of the Eucharist 1423 Panel, 24 x 38 cm Bowes Museum, Barnard Castle
	St Thomas Inspired by the Dove of the Holy Ghost 1423 Tempera on wood, 23,6 x 39 cm Szépmûvészeti Múzeum, Budapest
	St Thomas Inspired by the Dove of the Holy Ghost (detail) 1423 Tempera on wood Szépmûvészeti Múzeum, Budapest
	St Thomas Inspired by the Dove of the Holy Ghost (detail) 1423 Tempera on wood Szépmûvészeti Múzeum, Budapest
	St Thomas Inspired by the Dove of the Holy Ghost (detail) 1423 Tempera on wood Szépmûvészeti Múzeum, Budapest
	St Thomas Before the Cross 1423 Panel, 25 x 28,8 cm Pinacoteca, Vatican
	St Jerome (detail) 1423 Panel Pinacoteca Nazionale, Siena