The earliest poetry of a country is expressed first in prose by word of mouth. It is then put down first in writing in prose, and later versions sometimes change the prose into meter. Often the earlier prose version is lost and it is then concluded that a literature of a nation begins in verse.
Let us examine the form of the earliest Irish literature. The oldest stories in Irish literature center around the exploits of Cuchulinn, who is reputed to have died at the beginning of the Christian era. This means that the tale about him was told by word of mouth up till the time they were written down in the seventh or eighth century. The versions of a few centuries later are the copies we now have in the epic _Táin Bó Cualnge_. According to Edmund C. Quiggin's article on Irish Literature in the _Britannica_, the original Tain consisted of prose interspersed with rhythmical prose called rhetoric. Later metrical poems were largely substituted for the rhetoric. As Mr. Quiggin says, the Tain is of interest as showing the preliminary stage through which the epics of all other nations had gone. No doubt even the _Iliad_ was originally told in prose (and probably written in prose) while the verse versions are the latest we have of the story.
Eleanor Hull, in _A Text Book of Irish Literature_, also says in Vol. 1, p. 95, that there are few verse poems in the earlier _Táin Bó Cualnge_, most of the poetry being usually in declamatory prose style known as rosg, while in the later version long verse poems are frequent.
The earliest Teutonic verse was rather rhythmical prose, with some alliteration. It is often hard to distinguish Anglo-Saxon prose from Anglo-Saxon verse. Ælfric, who is regarded by many as one of the fathers of English prose, wrote his _Lives of the Saints_ in rhythmical prose, arranged in irregular lines just like our modern free verse. The reader may consult Professor Skeat's edition. This arrangement, needless to say, did not make poetry of it. But free verse, as we see, was written in England in 1000 A.D.
Dr. Edwin Guest, in his _History of English Rhythms_, says that the Anglo-Saxon writers sometimes gave a very definite rhythm to their prose, and he cites a few passages characterizing King William, from the Chronicle attributed to Wulfstan in the latter part of the eleventh century. Dr. Guest adds that in his opinion this rhythmical prose was one of the instruments in breaking up the alliterative system of the Anglo-Saxons. The passage he cites, however, is no more rhythmical than many passages in modern English prose. Anglo-Saxon prose, then, often was rhythmical, and even arranged like free verse, but it became genuine poetry only when the element of ecstasy was present. Even the middle-English impassioned alliterative prose poem, _The Wooing of Our Lord_, of the thirteenth century, does not differ much from Anglo-Saxon verse.