THE PERCEPTION OF THINGS. 127 



of falling asleep, may be interpreted as due to the rise (in 

 certain lower motor centres) of the ordinary * tonic ' tension 

 to the explosion-point, when the inhibition commonly ex- 

 erted by the higher centres falls too suddenly away. 



One possible condition of hallucination then stands 

 revealed, whatever other conditions there may be. Wlien 

 the normal paths of association betiveen a centre and other centres 

 are throivn out of gear, any activity tuhich may exist in the 

 first centre tends to increase in intensity until finally the point 

 may he reached at lohich the last inivard resistance is overcome, 

 aTid the full sensational process explodes* Thus it will happen 

 that causes of an amount of activity in brain-cells which 

 would ordinarily result in a weak consciousness may pro- 

 duce a very strong consciousness when the overflow of these 

 cells is stopped by the torpor of the rest of the brain. A 

 slight peripheral irritation, then, if it reaches the centres of 

 consciousness at all during sleep, will give rise to the dream 

 of a violent sensation. All the books about dreaming are 

 full of anecdotes which illustrate this. For example, M. 

 Maury's nose and lips are tickled with a feather while he 

 sleeps. He dreams he is being tortured by having a pitch- 

 plaster applied to his face, torn off, lacerating the skin of 

 nose and lips. Descartes, on being bitten by a flea, dreams 

 of being run through by a sword. A friend tells me, as I 

 write this, of his hair changing its position in his forehead 

 just as he 'dozed off' in his chair a few days since. In- 

 stantly he dreamed that some one had struck him a blow. 

 Examples can be quoted ad libitum, but these are enough. f 



* I say the ' normal ' paths, because hallucinations are not incompatible 

 with so7ne paths of association being left. Some hypnotic patients will 

 not only have hallucinations of objects suggested to them, but will amplify 

 them and act out the situation. But the paths here seem excessively nar- 

 row, and the reflections which ought to make the hallucination incredible 

 do not occur to the subject's mind. In general, the narrower a train of 

 ' ideas ' is, the vivider the consciousness is of each. Under ordinary cir- 

 cumstances, the entire brain probably plays a part in draining any centre 

 which may be ideationally active. When the drainage is reduced in any 

 way it probably makes the active process more intense. 



f M. A. Maury gives a number: op. cit. pp. 136-8. 



