By Hypnotism we understand here the nervous sleep brought on in many ways: by fixity of look, by visual concentration upon a brilliant object, by convergence of the axes of vision, by a sustained and monotonous sensation, by a vivid sensory impression such as that produced by the sound of a gong, by a brilliant light, etc. No one can be hypnotized against his will; but once a person has given himself up to an operator, and gone through the exercises by which the effect is obtained, the operator can put him to sleep at pleasure, and even without the subject's knowledge...