The numerous incantations which were inscribed on clay tablets and treasured in libraries, do not throw much light on the progress of medical knowledge, for the genuine folk cures were regarded as of secondary importance, and were not as a rule recorded. But these metrical compositions are of special interest, in so far as they indicate how poetry originated and achieved widespread popularity among ancient peoples. Like the religious dance, the earliest poems were used for magical purposes. They were composed in the first place by men and women who were supposed to be inspired in the literal sense; that is, possessed by spirits. Primitive man associated "spirit" with "breath", which was the "air of life", and identical with wind. The poetical magician drew in a "spirit", and thus received inspiration, as he stood on some sacred spot on the mountain summit, amidst forest solitudes, beside a' whispering stream, or on the sounding shore. As Burns has sung: The muse, nae poet ever fand her, Till by himsel' he learn'd to wander, Adown some trottin' burn's meander, An' no think lang: O sweet to stray, an' pensive ponder A heart-felt sang! Or, perhaps, the bard received inspiration by drinking magic water from the fountain called Hippocrene, or the skaldic mead which dripped from the moon. The ancient poet did not sing for the mere love of singing: he knew nothing about "Art for Art's sake". His object in singing appears to have been intensely practical. The world was inhabited by countless hordes of spirits, which were believed to be ever exercising themselves to influence mankind. The spirits caused suffering; they slew victims; they brought misfortune; they were also the source of good or "luck ". Man regarded spirits emotionally; he conjured them with emotion; he warded off their attacks with emotion; and his emotions were given rhythmical expression by means of metrical magical charms. Poetic imagery had originally a magical significance; if the ocean was compared to a dragon, it was because it was supposed to be inhabited by a storm-causing dragon; the wind whispered because a spirit whispered in it. Love lyrics were charms to compel the love god to wound or possess a maiden's heart--to fill it, as an Indian charm sets forth, with "the yearning of the Apsaras (fairies)"; satires conjured up evil spirits to injure a victim; and heroic narratives chanted at graves were statements made to the god of battle, so that he might award the mighty dead by transporting him to the Valhal of Odin or Swarga of Indra.