Ammonius is believed to have developed the Diatesseron with Tatian in the second century (about 150). It seems that Ammonius authored the titles to each section. These titles were taken by Eusebuis in the fourth century (after 314) and further developed into a system of comparison to prove that there were no contradictions between the gospels. He showed the harmony of the gospels by demonstrating every place where they agreed. He did this in a series of ten categories of comparison. He writes to Carpianus about his system.

 

Eusebius to Carpianus, (my) beloved brother in the Lord.
Greetings.

Ammonius the Alexandrian, through truly much labor and zeal, presented to us the Fourfold Harmony:¹ set in order
next to the Gospel According to Matthew were the similar-sounding² pericopes of the rest of the Evangelists, with
the inevitable result that the continuing sequence of the three was utterly destroyed concerning the interconnection³
of readings.

But so that, while preserving entire the rest of the whole and the sequence, you may know the proper place in each
Evangelist in which each is guided by love of truth to say like another, taking a starting-point from the work of the
above-mentioned man, I have formed for you ten lists⁴ in total, attached below.

Of these, the first contains numbers in which similar things were said by the four: Matthew, Mark, Luke, John (agree).
The second, in which the three: Matthew, Mark, Luke (agree).
The third, in which the three: Matthew, Luke, John (agree).
The fourth, in which the three: Matthew, Mark, John (agree).
The fifth, in which the two: Matthew, Luke (agree).
The sixth, in which the two: Matthew, Mark (agree).
The seventh, in which the two: Matthew, John (agree).
The eighth, in which the two: Luke, Mark (agree).
The ninth, in which the two: Luke, John (agree).
The tenth, in which each of them wrote in his own manner (agree).

  The Eusebian Tables were quite popular in both the East and West. But they seem to hold special favor in the Syriac Gospel MSS. Nineteen illuminated  pages are dedicated to the tables in the Rabbula Gospels of 586 AD. The letter of Eusebius to Carpianus is framed in a decorative palmate border. This illumination of the text was an artistic tradition flowing from the Diatesseron. We know this from a copy of the Diatesseron  made in the 16^th century in Tur Abdin (in present day southeast Turkey) and brought to Rome by an Armenian bishop. The manuscript found its way to Florence where it was studied by Danish art historian Carl Nordenfalk, who is a specialist in Celtic manuscripts. When he later re’examined an illuminated Celtic gospel book, the Book of Durrow, he saw similarities with the ancient Diatessaron of Tatian and Ammoinis. For example, in the Book of Durrow the emblems of the Evangelists precede each gospel  as in Diatessaron. He also noticed that the palmate borders which we generally associate with Celtis knots was preceeded by the Syriac art form evidenced in the Rabbula Gospels. The Book of Durrow was composed only a few years after the Rabbula Gospels in the last decade of the sixth century.  It is believed to be the first figurative painting in British art.

   This same tradition in figurative illumination of manuscripts appears again in a slightly later Celtic manuscript, the Gospel of Willibrord and again on the front page of the Book of Kells .

  We now know there was extensive contact between the Syriac and Coptic east and the British Isles. In a letter to king Charlemagne of France, the English monk Alcuin named the Celtic fathers pueri egyptiaci or the children of the Egyptians. The Celtic fathers looked upon St. Anthony as their pattern in asceticism. In the seventh century Antiphony of the Irish monastery of Bangor loud we read,

This house full of delight
Is built on the rock.
And indeed is the true wine
transplanted out of Egypt.

  Seven Coptic monks of Egypt  lived in Disert Uilag in west Ireland and are remembered in the Irish Litany of the Saints as witnesses of the close contact between the Western and Eastern Church.

 

  Theodore of Tarsus, who knew Syriac, was the seventh Archbishop of Canterbury, and his books brought the teachings of the Syriac school of Antioch to Anglo-Saxon Britain. These books seeded the artistic imagination of the British Isles.

 

  While the illuminated texts of the Syriac and Coptic traditions preceeded the Irish and English MSS, the latter developed the illuminated text tradition with unrivaled genius.

 

           Rabbula Gospel Eusebian table                                       Lindisfarne Eusebian table

Rabbula image of Mary and Jesus                                        Book of Kells image of Mary and Jesus

Rabbula frames of Eusebian Letter                     Book of Durrow Frame of Matthew