The manuscripts belonging to each of these versions, A, B, and C, have sufficient traits in common to place them in a group by themselves. The question of the relationship of these manuscripts to one another and of the character of the suppositional archetype from which they are all descended is a most intricate one and one which has given rise to considerable discussion. The question still awaits a definite answer, which may never be forthcoming, because of the disappearance not only of the first draft of the Táin, but also of that of some its later redactions. We must not overlook the possibility, either, of an otherwise faithful copyist having inserted in the text before him a passage, or even an entire episode, of his own fabrication. This, no doubt, happened not infrequently, especially in the earlier period of the copying of Irish manuscripts, and a single insertion of this kind, or the omission, intentionally or by oversight, of a part of the original from the copy might, it will easily be seen, lead one to conclude that there once existed a form of the story which as a matter of fact never existed.
The version of the Táin which I have chosen as the basis for my translation is the one found in the Book of Leinster (Leabhar Laighneach), a voluminous vellum manuscript sometime called the Book of Glendalough and now kept in the Library of Trinity College, Dublin, catalogue number H. 2. 18. Only a part of the original book remains. It dates from about the year 1150. This date is established by two entries in the manuscript itself: "Aed son of Crimthann (Hugh macGriffin) hath written this book and out of many books hath he compiled it" (facsimilé, at the bottom of page 313). Who this Aed was will be clear from the other entry. It appears that he had lent the manuscript while still unfinished to Finn macGorman,
Manuscripts, Edinburgh, 1912, pp. 174, 220; E. Windisch, Táin Bó Cúalnge, Einleitung und Vorrede, S. lx. ff.
