M. D'Arbois also traces the saga in Gaul in the fact that on the menhir of Kervadel Mercury is figured with a child, Mercury, in his opinion, being Lug, and the child Cúchulainn.437 On another altar are depicted (1) a woodman, Esus, cutting down a tree, and (2) a bull on which are perched three birds—Tarvos Trigaranos. The two subjects, as M. Reinach points out, are combined on another altar at Trèves, on which a woodman is cutting down a tree in which are perched three birds, while a bull's head appears in the branches.438 These represent, according to M. D'Arbois, incidents of the Táin—the cutting down of trees by Cúchulainn and placing them in the way of his enemies, and the warning of the bull by Morrigan in the bird form which she shared with her sisters Badb and Macha.439 Why, then, is Cúchulainn called Esus? "Esus" comes from a root which gives words meaning "rapid motion," "anger," "strength"—all shown by the hero.440 The altars were found in the land of the Belgic Treveri, and some Belgic tribes may have passed into Britain and Ireland carrying the Esus-Cúchulainn legend there in the second century B.C., e.g. the Setantii, dwelling by the Mersey, and bearing a name similar to that of the hero in his childhood—Setanta (Setantios) as well as the Menapii and Brigantes, located in Ireland by Ptolemy.441 In other words, the divine Esus, with his surname Smertullos, was called in Ireland Setanta, after the Setantii, and at a later date, Cúchulainn. The princely name Donnotaurus resembles Dond tarb, the "Brown Bull" of the saga, and also suggests its presence in Gaul, while the name (dêiotaros), perhaps the equivalent of De^uio-taruos, "Divine Bull," is found in Galatia.442 Thus the main elements of the saga may have been known to the continental Celts before it was localised in Ireland,443 and, it may be added, if it was brought there by Gallo-British tribes, this might account for the greater popularity of the native, possibly pre-Celtic, Fionn saga among the folk, as well as for the finer literary quality of the Cúchulainn saga. But the identification of Esus with Cúchulainn rests on slight grounds; the names Esus and Smertullos are not found in Ireland, and the Gaulish Esus, worshipped with human sacrifice, has little affinity with the hero, unless his deeds of slaughter are reminiscent of such rites. It is possible, however, that the episode of the Táin came from a myth explaining ritual acts. This myth may have been the subject of the bas-reliefs, carried to Ireland, and there worked into the saga.
The folk-versions of the saga, though resembling the literary versions, are less elaborate and generally wilder, and perhaps represent its primitive form.444 The greatest differences are found in versions of the Táin and of Cúchulainn's death, which, separate in the saga, are parts of one folk-tale, the death occurring during the fighting over the bull. The bull is his property, and Medb sends Garbh mac Stairn to take it from him. He pretends to be a child, goes to bed, and tricks Garbh, who goes off to get the bull. Cúchulainn arrives before him and personates the herdsman. Each seizes a horn, and the bull is torn in two.445 Does this represent the primitive form of the Táin, and, further, were the bull and Cúchulainn once one and the same—a bull, the incarnation of a god or vegetation spirit, being later made anthropomorphic—a hero-god whose property or symbol was a bull? Instances of this process are not unknown among the Celts.446 In India, Indra was a bull and a divine youth, in Greece there was the bull-Dionysos, and among the Celts the name of the divine bull was borne by kings.447 In the saga Morrigan is friendly to the bull, but fights for Medb; but she is now friendly, now hostile to Cúchulainn, finally, however, trying to avert his doom. If he had once been the bull, her friendliness would not be quite forgotten, once he became human and separate from the bull. When she first met Cúchulainn she had a cow on whom the Brown Bull was to beget a calf, and she told the hero that "So long as the calf which is in this cow's body is a yearling, it is up to that time that thou art in life; and it is this that will lead to the Táin."448 This suggests that the hero was to die in the battle, but it shows that the Brown Bull's calf is bound up his life. The Bull was a reincarnation of a divine swineherd, and if, as in the case of Cúchulainn, "his rebirth could only be of himself,"449 the calf was simply a duplicate of the bull, and, as it was bound up with the hero's life, bull and hero may well have been one. The life or soul was in the calf, and, as in all such cases, the owner of the soul and that in which it is hidden are practically identical. Cúchulainn's "distortion" might then be explained as representing the bull's fury in fight, and the folk-tales would be popular forms of an old myth explaining ritual in which a bull, the incarnation of a tree or vegetation spirit, was slain, and the sacred tree cut down and consumed, as in Celtic agricultural ritual. This would be the myth represented on the bas-reliefs, and in the ritual the bull would be slain, rent, and eaten by his worshippers. Why, then, should Cúchulainn rend the bull? In the later stages of such rites the animal was slain, not so much as a divine incarnation as a sacrifice to the god once incarnated in him. And when a god was thus separated from his animal form, myths often arose telling how he himself had slain the animal.450 In the case of Cúchulainn and the bull, the god represented by the bull became separate from it, became anthropomorphic, and in that form was associated with or actually was the hero Cúchulainn. Bull sacrifices were common among the Celts with whom the bull had been a divine animal.451 Possibly a further echo of this myth and ritual is to be found in the folk-belief that S. Martin was cut up and eaten in the form of an ox—the god incarnate in the animal being associated with a saint.452 Thus the literary versions of the Táin, departing