Moreover, the doctrine is still in process of enlargement. Very convincing conclusions may be drawn from these facts. The subject is obscure and difficult, but if the inception of the process of breaking down the right of enforcing the blood feud be fixed provisionally toward the middle of the tenth century,--and this date is early enough,--the movement of thought cannot be said to have attained anything like ultimate results before at least the year 1321 when a case is cited wherein a man was held guilty because he had attempted to kill his master, and the “_volunias in isto casu reputabitur pro facto_.” Measuring by this standard five hundred years is a short enough period to estimate the time necessary for a community to pass from the stage when the blood feud is recognized as unquestioned law, to the status involved in the administration of the cities of refuge, for in these cities not only the mental condition is provided for as a legitimate defence, but the defence of negligence is made admissible in a secular court. “These six cities shall be a refuge, both for the children of Israel, and for the stranger, and for the sojourner among them; that every one that killeth any person unawares may flee thither.... “If he thrust him of hatred, or hurl at him by laying of wait that he die; “Or in enmity smite him with his hand, that he die: he that smote him shall surely be put to death; for he is a murderer: the revenger of blood shall slay the murderer, when he meeteth him. “But if he thrust him suddenly without enmity, or have cast upon him anything without laying of wait, “Or with any stone, wherewith a man may die, seeing him not, and cast it upon him, that he die, and was not his enemy, neither sought his harm: “Then the congregation shall judge between the slayer and the revenger of blood according to these judgments: “And the congregation shall deliver the slayer out of the hand of the revenger of blood, and the congregation shall restore him to the city of his refuge, whither he was fled.”... [Footnote: Numbers XXXV, 15, 20-25.]