As a matter of fact, each great sanctuary seems to have had its own collection. These were added to from time to time; some of them were amalgamated together, or parts belonging to one collection were incorporated into another. Spells which had been found effective in warding off disease or preventing evil, were introduced into a collection which related to the same subject, whatever may have been their source, and the list of gods invoked was continually being enlarged, in the hope that some one at least among them might give the sufferer relief. The older collections were modified in accordance with the requirements of the State religion, and the animism that inspired them accommodated to the orthodox belief; while new collections came into existence which breathed the later Semitic spirit, and were drawn up under the supervision of the Babylonian priesthood. Hymns and even penitential psalms were embodied in them, like the verses of the Bible or the Quran, which are still used as charms in Christian and Mohammedan countries; and it is sometimes difficult to distinguish between the hymn that served merely as an incantation and the hymn that was chanted in the service of the gods. Indeed, incantatory formulæ are not unfrequently intermixed with the words of the hymn or psalm, producing that grotesque and embarrassing medley of exalted spiritual thought and stupid superstition which so often meets us in the religious literature of Babylonia. How late some of the collections are in the history of Babylonian religion, may be judged from the fact that a time came when the old Sumerian language was no longer considered necessary to ensure the efficacy of the charm, and collections of incantations were made in the Semitic language of later Babylonia. Criticism will hereafter have to sift and distinguish these collections one from the other, and, above all, determine the earlier and later elements contained in each. At present such a task is impossible. Few, if any, of the collections have come down to us in a perfect state; there are many more, doubtless, which future research will hereafter bring to light; and as long as we are dependent solely on the copies made for the library of Nineveh, without being able to compare them with the older texts of the Babylonian libraries, the primary condition of scientific investigation is wanting. Nevertheless there are certain collections which stand out markedly from among the rest. They display features of greater antiquity, and the animism presupposed by them is but thinly disguised. It is comparatively easy to separate in them the newer and older elements, which have little in common with each other. Most of them point to Eridu as the source from which they have been derived, though there are others the origin of which is probably to be sought at Nippur.