Nevertheless, the forms of _poetry_ exhibit an important advance over those of the more primitive peoples just mentioned. Particularly in the case of the _song_, we find that the simple expression of the moods directly aroused by nature is supplemented by a further important feature. This feature is closely bound up with that more lively bodily and mental activity of totemic culture which is reflected likewise in its use of implements and weapons. Karl Bücher was the first to point out that common labour gives rise to common songs, whose rhythm and melody are determined by the labour. The increasing diversity of the work results in a wider range of content and also in a richer differentiation of forms. Such _work-songs_ are to be found throughout the entire totemic era, whereas, of course, they are lacking in the preceding age, in which common labour scarcely exists. Contemporaneously with the work-song, the _cult-song_ makes its appearance. The latter is essentially conditioned by the development of totemic ceremonies. As these become more numerous, the cult-song likewise gradually grows richer and more manifold, in close reciprocal relations with the dance and music. In the case of the cult-song, as well as of the work-song, the above-mentioned repetition of motives comes to exercise an important influence on the accompanying activity. Though different causes are operative in the two cases, these causes nevertheless ultimately spring from a _single_ source--namely, the heightening of emotions. In the cult-song, man aims to bring his petitions and, as we may say for the earlier age, the magic which his words exercise, as forcibly as possible to the notice of the demons or, at a later period, of the gods whom he addresses. For this reason the same wish is repeated again and again. The most primitive form of cult-song generally consists of but a single wish repeated in rhythmic form. In the work-song, on the other hand, it is the constantly recurring rhythm of the work that leads directly to the repetition of the accompanying rhythmic and melodic motives. When one and the same external task becomes associated time and again with these accompanying songs, the two mutually reinforce each other. The song is a stimulus to the work, and the work heightens the emotion expressed in the song. Both results vary with the degree in which the song is adapted to the work and thus itself becomes a poetic representation of it. Here again neither plan nor purpose originally played the least part; the development was determined by the rhythmic and melodic motives immanent in the work. Several brief illustrations may serve to give us a clear picture of what has been said. The first is a cult-song of American origin. Again we turn to the cult usages of one of the tribes of New Mexico, the Sia. The motif of the song, which is rain-magic, furnishes the material for very many of the ceremonies of these regions. The song of the rain-priests is as follows:--