PSYCHO-PHYSICAL PHENOMENA 475 



r esuvius and of his legs being scorched by the lava. In this case 

 the unaccustomed sensation! of warmth at his feet produced a com- 

 plex oneiric current with a wealth of varied hallucinatory images. 



Dreams are more often incited by internal sensations of 

 physiological needs (hunger, thirst, desire to micturate, sexual 

 impulse) than by external sensations. 



Bierre de Boismont relates that in the thirst endured by the 

 crucified in Jerusalem " they frequently dreamed " (oneiric 

 imagination) "of the cool fountains of their native country." 

 When Napoleon's army began to suffer from hunger in Eussia, 

 many soldiers were tormented by dreams of assuaging their 

 appetite in their distant homes. 



When the tension in the bladder produces the desire to 

 micturate, nocturnal incontinence of urine occurs in children and 

 also in certain adults, because they dream of voluntarily passing 

 urine. Erotic dreams, which are so frequent in adolescence, are 

 often caused by memories of the charmers of the previous day ; 

 but in celibates they are frequently due to the tension of the 

 seminal vesicles, associated with hyperaemia of the genitalia, 

 promoted by the warmth of the bed. When the erotic dream is 

 accompanied by ejaculation the venereal paroxysm not infrequently 

 produces awakening. 



Dreams are to a large extent promoted by the hallucinatory 

 images which, as we have seen, are not infrequently present in 

 the drowsiness that precedes sound sleep (Maury's hypnagogic 

 hallucinations') and in the waking-sleeping state that precedes 

 awakening (Myers' hypnopompic hallucinations). Dreams domin- 

 ated by visual hallucinations are the most frequent ; those due 

 to auditory hallucinations are less common; those started by 

 tactile, gustatory, and olfactory sensations, still more rare. This 

 difference in the frequency of hallucinations of the special senses 

 is probably related to the ease with which the respective images 

 are called up in memory. 



From the psychological point of view more interest attaches 

 to dreams produced by the functional state of the organs, both 

 under normal and under pathological conditions. 



Normally, the visceral functions do not give rise to any 

 definite sensation in the waking state, although they participate 

 in the formation of the common bodily sense or coenaesthesia. . 

 During sleep, on the contrary, the partial or total suspension of 

 external sensations favours the development and increases the 

 intensity of the internal sensations, and gives rise to a number 

 of dreams. The dreams due to abnormal disorders of the viscera 

 are particularly vivid, even before these are sufficiently pronounced 

 to be noticed in the waking state. Aristotle, indeed, declared 

 that incipient organic disorders might be manifested in dreams 

 and be the precursors of disease. 



