Numerous methods of inducing the hypnotic state have been employed. The greater number consist in artificial modification of the condition of the brain through the agency of sensory impressions originated upon the periphery of the body. The simplest form of such influence is presented by the results of gentle friction of the skin with the palm of the hand or the tips of the fingers. Many an aching head has thus been relieved, many a restless sufferer soothed to sleep. In like manner, a susceptible subject may be hypnotized by any continuous and gentle excitement of the senses of sight, hearing, and touch. Concentration of the attention upon a brilliant object, like a piece of polished metal or a small mirror, especially if it be placed a little above the level of the eyes, and so near that considerable convergence of the eyeballs is necessary for distinct vision, affords a very efficient means of inducing artificial somnambulism. Certain persons may be readily hypnotized by gently pressing the eyelids together, and at the same time making slight pressure upon the eyeballs. Others pass into this condition by merely closing their eyes, and remaining motionless in a quiet room. The phenomena of artificial somnambulism are frequently developed through the agency of impressions derived directly from the sphere of consciousness. The intellectual effort of trying to sit still and think of nothing is sometimes sufficient to induce the hypnotic state. The ordinary devices by means of which wakeful people are taught to beguile sleep, by counting, or by repeating long lists of names, etc., all belong to this category. Compulsory attention to any continuous intellectual process, like adding up a column of figures, or trying to read a dull book, is sometimes effectual. If, with these, or with similar acts of attention, be associated the expectation that something unusual is about to occur, as when the individual is aware of being the subject of an experiment, the evolution of the somnambulic condition is greatly facilitated. Thus, one of the most recent methods, consists in merely sitting, for half an hour or more, with the back towards the patient. Attention, curiosity, and expectation, are thus excited, and a susceptible person soon begins to manifest some of the numerous and various forms of the hypnotic state. Heidenhain caused one of his students thus to go to sleep in broad daylight, by simply assuring him that he should hypnotize him from a distance at a particular hour of the afternoon. The monks of Mt. Athos were accustomed to hypnotize themselves by fixing their eyes and their thoughts upon the navel; hence the reputation of omphaloscopy as an aid to ecstatic meditation.