ix SCIENTIFIC HYPNOSIS AND THE OCCULT 341
or less mechanical nature, is supposed to interfere with the activity of the brain and to leave only the lower motor centres active. However, as far as the physiological changes can be observed in the normal sleeper, it is found that the physiological changes follow drowsiness and sleep rather than the reverse.
Chemical Theories.Toxins are produced as waste products of metabolism and they produce the same effect as drugs. However the individual can be awakened, or by an effort of will he can postpone drowsiness. This does not apply to the effect of drugs.
Histological Theories.The neural cells become congested, cannot communicate with one another and therefore sleep ensues.
Biological Theories.Plants and the lower animals go through a periodical rhythm. Sleep is not a passive state but active and instinctive, a specific reaction to the stimulus of darkness. People who wandered about in the dark were less likely to survive and leave descendants than those who slept in security.
Loss of Interest.Bergson and Rignano support this theory. To sleep says Bergson is to disinterest oneself. We sleep in direct proportion to our disinterestedness. The fact that a sleeper before passing into the stupor can decide that a certain stimulus, and that only among ordinary stimuli, shall awaken him, gives strength to this theory.
The physiological criterion of the patellar reflex or the knee-jerk, which disappears in normal sleep, shows the hypnotic trance to be allied, rather, with the waking state, and to be clearly differentiated not only from sleep but from incipient drowsiness as well, according to Bass.13 The psychological test of voluntary reaction to a signal shows practically identical results. Moreover, the same techniques which distinguished hypnosis from sleep were