no THE POPULAR SCIENCE MONTHLY, 



the consideration that with the temporary abolition of consciousness 

 the inhibitory influence, which we know the higher nerve-centers to 

 be capable of exerting upon the lower, is presumably suspended. But 

 quite unanticipated is the remarkable fact that the state of exalted reflex 

 excitability may persist for several days perhaps for a week after a 

 man has been aroused from a state of profound hypnotism. Thus, 

 Dr. Krener, after having been hypnotized by Professor Heidenhain, 

 and while asleep made to bend his arm twice, for several days after- 

 ward was unable again to straighten it, on account of the flexor mus- 

 cles continuing in a state of tonic contraction, or cramp. In these 

 experiments Heidenhain found that a very gentle stimulation of the 

 skin caused only the muscles lying immediately below the seat of stimu- 

 lation to contract, and that on progressively increasing the strength of 

 the stimulus its effect progressively spread to muscles and to muscle- 

 groups farther and farther removed from the seat of stimulation. It 

 is interesting that this progressive spread of stimulation follows al- 

 most exactly Professor Pfluger's law of irradiation. But the rate at 

 which a reflex excitation is propagated through the central - nerve 

 organs is very slow, as compared with the rapidity with which such 

 propagation takes place in ordinary circumstances. Moreover, the 

 muscles are prone to go into tonic contraction, rather than to respond 

 to a stimulus in the ordinary way. The whole hypnotic condition thus 

 so strongly resembles that of catalepsy that Heidenhain regards the 

 former as nothing other than the latter artificially induced. In the 

 case of strong persons this tonic contraction of the muscles may make 

 the body as stiff as a board, so that, if a man is supported in an horizon- 

 tal position by his head and his feet only, one may stand upon his 

 stomach without causing the body to yield. The rate of breathing 

 has been seen by Heidenhain to be increased fourfold, and the pulse 

 also to be accelerated, though not in so considerable a degree. 



In a chapter on the conditions which induce the state of hypnotism, 

 Heidenhain begins by dismissing all ideas of any special " force " as 

 required to produce or to explain any of the phenomena which he has 

 witnessed. He does not doubt that some persons are more susceptible 

 than others to the influences which induce the hypnotic state, and he 

 if^hinks that this susceptibility is greatest in persons of high nervous 

 sensibility. These " influences " may be of various kinds ; such as 

 looking continuously at a small bright object, listening continuously to 

 a monotovious sound, submitting to be gently and continuously stroked 

 upon the si^in, etc. the common peculiarity of all the influences which 

 may induce ^i^g hypnotic state being that they are sensory stimuli of 

 a gentle, continuous, and monotonous kind. Awakening may be pro- 

 duced by suOf-iguiy blowing upon the face, slapping the hand, scream- 

 ing in the ear, etc., and even by the change of stimulus proceeding 

 from the retma -^hich is caused by a person other than the operator 

 suddenly taking i^ig pi^ce before the patient. On the whole, the hyp- 



