But who is the bond of their union? It pleased the Divine Providence that, even before St. Ignatius wrote, and even in the lifetime of the Apostle who recorded the commission to feed the whole flock of Christ, the harmony and obedience of which St. Ignatius spoke should be broken in a particular diocese, and that St. Peter's third successor should execute his office and assert the Divine commission by fulfilling it. His conduct in this marks, by a solemn act, the line between the Apostolate and the Primacy. That he speaks in the name of the whole Roman Church, as the voice of a Body, illustrates further the words of St. Ignatius, "Your presbytery is fitted as exactly to the bishop as the strings are to a harp."[54] In the testimony of these Apostolic Fathers, each completing the other, we have not only the local bishop planted as the unit of the Church's organism in any particular city, but the bishop who sits in the See of Peter, the tie and bond of his brethren. The harp sounds its notes to Christ throughout the world. Another point in which their testimony exactly agrees is, that while St. Clement speaks of the government of the Church as enacted with even greater accuracy and enforced with even stronger penalties than the law of Moses, St. Ignatius takes the strict observance of unity and obedience to external authority as a perfect test of the inward disposition, a perfect assurance that those who exercised these virtues were members of Christ. The temper in which these Fathers write is as far as possible removed from the notion that Church government was either lax or uncertain. To them it comes from above, and requires inward obedience, as the appointment of Christ. Eusebius, the first historian of the Church, compiling about the year 324 notices of the times before him, with, records at his command which are no longer extant, describes in the following terms the first period, that in which the Apostles themselves preached, which we may speak of as running from the Day of Pentecost to the destruction of Jerusalem:—