If Hegesippus can be held to have referred to the Diates 2. The legends of the Christianizing of Edeasa, older than Eusebius, mention the Diatessaron as the chief sacred book alongside the Old Testament. In the Syriac translation of the Hist. In the fifth century there was a definite rejection of the Diateasaron and exclusion of it from use in service, and that without distinction of party affiliations of the bishops who directed the movement. But from near Mosul to the bishopric of Kyros the Diatessaron must have been for the churches long the service-book in the Gospels, while the translations of the separate Gospels were used in the studies of the theologians, a condition which prevailed at least till about 370 A.D., when Ephraem Syrus lectured ,upon the Diatessaron with only occasional references to the canonical Gospels.
Similar evidence comes from other writers.
Apart from the two translations already mentioned, the history of the Diatessaron seems to have run its course entirely in the region of Syria. And it is to be noted that in its original form it was Greek, and was translated into the Syriac. The lack of any testimony for its existence among the Greek churches and the way in which Greek writers refer to it confirm the conclusion already reached. That Tatian, the writer of an apology in Greek, if he was in any event the author of the Diatessaron. could have written it only in Greek is 3. The an opinion founded upon ignorance of Diatessaron historical facts.