In the first place, then, it is important to bear in mind that the numerous spirits, when introduced into the religious and other texts, are almost invariably preceded by a sign--technically known as a determinative--which stamps them as divine. This sign being the same as the one placed before the names of the gods, it is not always possible to distinguish between deities and spirits. The use of a common sign is significant as pointing to the common origin of the two classes of superior powers that thus continue to exist side by side. A god is naught but a spirit writ large. As already intimated in a previous chapter, a large part of the development of the Babylonian religion consists in the differentiation between the gods and the spirits,--a process that, beginning before the period of written records, steadily went on, and in a certain sense was never completed. In the historical texts, the gods alone, with certain exceptions, find official recognition, and it is largely through these texts that we are enabled to distinguish between the two classes of powers, the gods and the spirits; but as a survival of a primitive animism, the demons, good, bad, and indifferent, retain their place in the popular forms of religion. Several hundred spirits occur in the incantation texts, and almost as many more in other religious texts. We may distinguish several classes. In the first place, there are the demons that cause disease and all manner of physical annoyances. The chief of these will be considered when we come to the analysis of the incantation texts. Against these demons the sufferer seeks protection by means of formulas, the utterance of which is invested with peculiar power, and again by means of certain rites of an expiatory or purificatory character. Next, we have the demons supposed to inhabit the fields, and to whom the ground is supposed to belong. These were imaged under various animal forms, serpents and scorpions being the favorite ones. When possession was taken of the field, the spirits inhabiting it had to be propitiated. The owner placed himself under their protection, and endeavored to insure his rights against wrongful encroachment by calling upon the demons to range themselves on his side. It was customary, especially in the case of territory acquired by special grant of the monarch, or under extraordinary circumstances, to set up a so-called boundary stone,[213] on which the owner of the field detailed his right to possession, through purchase or gift, as the case may be. This inscription closed with an appeal to various gods to strike with their curses any intruder upon the owner's rights. In addition to this, the stones are embellished with serpents, scorpions, unicorns, and various realistic or fantastic representations of animal forms. These, it would seem, symbolize the spirits, the sight of which, it was hoped, might act as a further and effectual warning against interference with the owner's rights.[214]