 In 1888, Pope Leo XIII issued a letter to the Bishops of Brazil, "In plurimis", and another in 1890, "Catholicae Ecclesiae" (On Slavery In The Missions).In both these letters the Pope singled out for praise twelve previous Popes who had made determined efforts to abolish slavery.Maxwell (1975) notes that Leo did not make mention of conciliar or Papal documents, nor canons of the general Church Law that had previously sanctioned slavery.