Irenaeus is succeeded closely by Clement of Alexandria, Clement by Tertullian, Tertullian by Hippolytus and Origen, and the testimony which these writers bear to the Gospel is marvellously abundant and unanimous.
I calculate roughly that Irenaeus quotes directly 193 verses of the first Gospel and 73 of the fourth.

Clement of Alexandria and Tertullian must have quoted considerably more, while in the extant writings of Origen the greater part of the New Testament is actually quoted [Endnote 315:1].
But more than this; by the time of Irenaeus the canon of the four Gospels, as we understand the word now, was practically formed.

We have already seen that this was the case in the fragment of Muratori.

Irenaeus is still more explicit.

In the famous passage [Endnote 315:2] which is so often quoted as an instance of the weak-mindedness of the Fathers, he lays it down as a necessity of things that the Gospels should be four in number, neither less nor more:-- 'For as there are four quarters of the world in which we live, as there are also four universal winds, and as the Church is scattered over all the earth, and the Gospel is the pillar and base of the Church and the breath (or spirit) of life, it is likely that it should have four pillars breathing immortality on every side and kindling afresh the life of men.