The effects themselves were certainly observed in all times. Even the phenomena of hypnotism date probably back some thousands of years, however difficult it may sometimes be to discriminate between the artificial hypnotic states and hysteric or hystero-epileptic occurrences in the past. Certainly it may be acknowledged that the Yogi in India cultivated in the most remote times the methods of autosuggestion which evidently led to hypnotic states, and everywhere around the Mediterranean, antiquity knew the hypnotizing effect of staring on polished metals and crystals. So in Egypt, so in Greece and Rome; and it has often been claimed that the priestesses of Delphi and the sibyls of the Romans were in states of hystero-hypnotic character. As to the therapeutic use, especially the Greek physicians applied hypnotic means. Excited patients were brought to repose by methods of stroking. The efforts to explain scientifically the mysterious powers which men can gain over the mind and will of another begin at the end of the Middle Age and were developed quite naturally from the prevailing astrological doctrines. Astrology worked on the theory that the human fate depends upon the stars. These stars have an effect on the human organism. That proves that an influence can exist between distant bodies. It is, therefore, not more surprising that one organism can also have an influence on another organism. Well known since antiquity were such influences from one object to another, as in the case of the magnet. Thus there may be a kind of magnetic power which creates relations between all objects in the universe. Pomponnazi explained thus at the end of the fifteenth century the therapeutic effects of the human soul by the mutual influence which stars and men have on each other. This theory comes to much more important development in the writings of the physician Paracelsus. One individual by the power of his effort can influence the will of another individual, can fight with it, and suppress it; and all through energies which are analogous to the magnetic power which binds stars and men. In the middle of the seventeenth century, Helmont connects this power of magnetic attraction and repulsion with an ethereal element which penetrates all bodies and keeps them in motion. Through it man, too, can by his mere imagination work on other men. This will can also be effective on drugs which get through it a special therapeutic power. Somewhat different was the theory of a Scotch physician, Maxwell, in the second half of the seventeenth century. The ethereal spirit, which is identical with light, can be artificially cumulated in any organism and that secures its health. As one man can influence this vivifying ether in any other man, he can produce cures even from a great distance. All diseases are merely reductions of this ethereal spirit in the organism.