As in this investigation we are no longer concerned with the abstract and ideal work of art, it seems that we may now reasonably appeal to those theories which we before found inadequate only because they did not account for the purely æsthetic qualities of artistic activity. The play-impulse, the impulse to attract by pleasing, the imitative impulse, etc., although they give us no information as to the essentially artistic criterion, may nevertheless have called into existence works and manifestations which fulfil the requirements of the several art-forms. Man may have composed dramas, may have painted pictures, may have made poems, in play, or out of the desire to please, or out of the inborn taste for mimicry. In particular the play-impulse must, as we have already admitted in the first part of this work, be dealt with as a factor of incalculable importance in the history of art. In his conclusive researches on animal and human play Professor Groos has succeeded in showing that the chief classes of art-forms are already foreshadowed in the various forms of experimentation—that most general and most important kind of play which can be observed not only among children, but even among the higher animals.[173] In the outcome of this simple and common activity we have, it may be said, a sufficient bulk of raw material of which the art-impulse, when once fully developed, can avail itself in order to fulfil its own essentially artistic purposes. And it would therefore seem as if there were no further problem to be solved with regard to the evolution of art. Adherents of this view may, moreover, point to the fact that, apart from all the motive factors represented by the various non-æsthetic impulses, the development of art has been favoured by influences of a more passive or static character. It has evidently been of vital importance to the evolution of architecture and decoration that things of useful nature have provided these arts with a kind of concrete frame within which to display their manifestations. The effects of this material condition are so much the greater because with his constitutional conservatism man—whether civilised or primitive—always allows himself to be bound by old forms long after he has relinquished the technical procedures which have originally called these forms into existence. By the scientific “biological” researches on decorative art it has been conclusively shown how great a portion of the ornamental “store” consists of lines and combinations of lines which have quite automatically been borrowed from an earlier technique. Decorative motives, which to the uninitiated observer appear as products of spontaneous artistic activity, thus reveal themselves to the historical student as unintentional by-products of work. Where earlier investigators assumed an æsthetic composition, modern researches refer to the force of mental inertia and the cravings of expectant attention.[174]