FUNCTIONS OF THE ENCEPHALOIST. 213 



ganglia which, immediately govern the heart, are in con- 

 tinual action, while others, including the cerebral hemi- 

 spheres, require considerable pauses for the renewal of their 

 activity. 



Dreams, like sleep, are only imperfectly understood. Their 

 main peculiarity consists in a certain amount of mental 

 activity existing, with complete or almost complete cessation 

 both of impressions from the organs of sense, and of voli- 

 tionary impulses to the muscles. In these circumstances, 

 the pictures of memory and imagination come into the fore- 

 ground, unrepressed by the stronger representations of sense, 

 and assume the appearance of reality. One idea suggests 

 another, and each one which is sufficiently vivid has in turn 

 the semblance of reality; and from this arise the strange 

 shifting of scenes and curious confusions with which every 

 one is familiar. 



Apparitions, and other illusions from mental causes, are to 

 be accounted for in a similar way. Many well authenticated 

 instances are on record of figures appearing to persons other- 

 wise perfectly sane. Among them may be mentioned the 

 case of Nicolai, the Berlin bookseller, who saw persons in 

 the room with him, when he knew that there was in reality 

 no one present; but so far from being disturbed by these 

 apparitions, made them the subject of study and recorded 

 the details. In his case, they were traced to the neglect 

 of a customary bloodletting, and disappeared after leeching. 

 In such rare occurrences there is the same prominence of a 

 mental picture as occurs in dreams; but, in dreams, that 

 prominence results from the absence of sensations origi- 

 nated by contact with the outer world; while, in appari- 

 tions, it is the consequence of some pathological action within 

 the brain. 



In somnambulism, the mind is likewise occupied as in a 

 dream; but the ideas which possess it, while others have been 

 excluded, become so strong that the apparatus of voluntary 

 movement and of the senses are thrown into action in an 

 automatic fashion, the attention being directed to the all 

 absorbing imagination. The 'mesmeric trance is a very similar 

 condition, in which the will is altogether governed by the 

 ideas impressed by another person. 



