340 PSYCHOTHERAPY : SCIENTIFIC AND RELIGIOUS chap.
induced positive hallucinations (seeing things which are not present), negative hallucinations (being functionally blind to things really present), hypnotic anaesthesias, hypnotic analgesias (insensibility to pain), and the action of post-hypnotic suggestion had all been clearly described.
' The hypnotic sleep may be light (hypnoidal), deep, or that of the state of somnambulism. The light and deep sleep closely resemble ordinary sleep, but the somnambulism is somewhat different. I f an ordinary sleeper is spoken to, he is usually aroused by the stimulating effect of the sound conveyed to the brain, through the auditory nerves, but in the somnambulant state he can be spoken to without being disturbed, and, on the contrary, the effect is actually soothing. Whereas in natural sleep the patient is to a very great extent out of touch with the external world, in hypnotic somnambulism he is, in fact, in touch with (en rapport) the outer world through the hypnotist, and is able to concentrate to a high degree in his response to suggestions made.
In normal sleep the body is closed for repairs ; as soon as all these repairs are done, the normal healthy person wakes up with renewed energy. The hypnotic state may be brought about at any time of the day, and long before any perceptible inroad has been made on the store of nervous energy laid up during previous natural sleep. It follows that during this artificially produced sleep which is the hypnotic state there may be great accumulation of an excess of energy, all of which can be concentrated and directed into any channels the hypnotist desires.
At present there is no satisfactory theory to explain the phenomena of sleep, though most of the theories give partial explanations. The main theories are as follows :
Physiological.Some physiological change of a more