The power acquired over a freeman by the mancipatio. To form a clear conception of the true import of the word in the Roman juris- prudence, it is necessary to advert to the four distinct powers which were exercised by the pater familias, viz.; the manus, or martial power; the mancipium, resulting from the mancipatio, or alienatio per cæs et libram, of a freeman; the dominica potes- tas, the power of the master over his slaves, and the patria potestas, the paternal power. When the pater familias sold his son, venum dare, mancipare, the paternal power was succeeded by the mancipium, or the power acquired by the purchaser over the person whom he held in mancipio, artd whose condition was assimilated to that of a slave. What is most remarkable is, that on the emancipation from the mancipium he fell back into the paternal power, which was not entirely exhausted until he had been sold three times by the pater familias. Si pater filium ter venum dat, filius a patre liber esto. Gaius speaks of the mancipatio as imaginaria quædam venditio, because in his times it was only resorted to for the purpose of adoption or emancipation. See 1 Ortolan, 112; Morey, Rom. L. 28, 33; Sohm, Inst. R. L. 124, 390; ADOPTION;