Plural of fidei commissium. A trustee: a factor. Trusts. By the civil law, no one could take any benefit under a will or testament unless he had testamenti factio with the testator. But as it often happened that a testator desired to benefit some one under his will, who had not this testamenti fiictio, the plan was adopted of appointing someone who had as the heir, enjoining him at the same time to transfer to the person really to be benefited the legacy or property, whatever it might be, which the testator wished to leave to him. Such injunctions the heir was not bound by the civil law to regard ; and as they were entrusted thus to his honor and good faith, they were called fidei-commissa. At a later period the heir could be compelled to fulfill the purposes of any trust reposed in him. Nothing is more common in the practice of our law, than for testators to dispose of their estate by trust-deed, and the trustee, once accepting, is bound to carry out all its purposes.