Contrary to the general impression, faith does not seem to be an essential element of success, at least on the part of the patient, for infants and very young children have been rendered clairvoyant as well as grown persons. On the other hand, natural susceptibility is indispensable, for Deleuse (_Déf. du Magnétisme_, p. 156) states that in his extended practice he found only one out of twenty persons fit to be magnetized. Of those whom he could influence, only one in twenty could converse in his sleep, and of five of this class not more than one became fully clairvoyant. Certain persons, though well endowed, impress their patients unfavorably, cause a sensation of cold instead of heat in their system, and produce a feeling of strong aversion. The most remarkable feature in all these relations, however, is the fact that the patient not unfrequently affects the magnetizer, and this in the most extraordinary manner. One physician took into the hand with which he had touched a dying person, two finches; they immediately sickened and died a few days later. Another, a physically powerful and perfectly healthy man, who was treating a patient suffering of _tic douloureux_ by means of magnetism, became unwell after a few days, and on the seventh day fell himself a victim to that painful disease, till he had to give up the treatment. He handed his patient over to a brother physician, who suffered in the same manner, and actually died in a short time. After continued practice has strengthened the magnetizer, his "passes" often become unnecessary, and he can at last, under favorable circumstances, produce magnetic sleep by a simple glance or even the mere unuttered volition. Some physicians had only to say Sleep! and their patient fell asleep; others were able to move the sleepers from their beds by a slight touch with the tip of the thumb. One of this class, after curing a poor boy of catalepsy, retained such perfect control over him that he only needed to point at him with his finger, or to let him touch some metal which he had magnetized, in order to make him fall down as if thunderstruck. The great German writer, known as Jean Paul, relates of himself that he, "in a large company and by merely looking at her fixedly, caused a Mrs. K. twice to fall almost asleep and to make her heart beat and her color go, till S. had to help her." The Abbé Faria, who seems to have been specially endowed with such power, would magnetize perfect strangers by suddenly stretching out his hands and saying in an authoritative tone: Sleep, I will it! He had a formidable competitor afterwards in Hébert, who played almost at will with a large number of spectators in his crowded hall, making them follow him wherever he led, or causing them to fall asleep by simply making passes over the inside of their hats. In the case of young girls he produced rigidity of members with great facility, and then caused them to assume any position he chose; his patients were utterly helpless