18 We have, however, in Our mind, in a matter of the same kind, another care which gives Us no light anxiety and presses upon Our solicitude. This shameful trading in men has, indeed, ceased to take place by sea, but on land is carried on to too great an extent and too barbarously, and that especially in some parts of Africa. For, it having been perversely laid down by the Mohammedans that Ethiopians and men of similar nations are very little superior to brute beasts, it is easy to see and shudder at the perfidy and cruelty of man. Suddenly, like plunderers making an attack, they invade the tribes of Ethiopians, fearing no such thing; they rush into their villages, houses, and huts; they lay waste, destroy, and seize everything; they lead away from thence the men, women, and children, easily captured and bound, so that they may drag them away by force for their shameful traffic. These hateful expeditions are made into Egypt, Zanzibar, and partly also into the Soudan, as though so many stations. Men, bound with chains are forced to take long journeys, ill supplied with food, under the frequent use of the lash; those who are too weak to undergo this are killed; those who are strong enough go like a flock with a crowd of others to be sold and to be passed over to a brutal and shameless purchaser. But whoever is thus sold and given up is exposed to what is a miserable rending asunder of wives, children, and parents, and is driven by him into whose power he falls into a hard and indescribable slavery; nor can he refuse to conform to the religious rites of Mahomet. These things We have received not long since with the greatest bitterness of feeling from some who have been eyewitnesses, though tearful ones, of that kind of infamy and misery; with these, moreover, what has been related lately by the explorers in equatorial Africa entirely coincides. It is indeed manifest, by their testimony and word, that each year 400,000 Africans are usually thus sold like cattle, about half of whom, wearied out by the roughness of the tracks, fall down and perish there, so that, sad to relate, those traveling through such places see the pathway strewn with the remains of bones.
Source: In Plurimis (Vatican.va)