372 HYPNOTISM. 



is situated elsewhere. The sensations due to the object are 

 not j^erceived, because they do not correspond with the 

 present mental phenomena. 



Just as in the case of positive, these negative hallucina- 

 tions may be suppressed by the evidence of the other senses, 

 or if sufficiently strong, associated negative hallucinations 

 occur. 



It remains to speak of visual illusions. These may be 

 defined as visual hallucinations which are due to suggestion 

 from the object which is seen, and not to auto-suggestion or 

 to suggestion received through any other sense. Further, 

 the hallucination so excited is always the sum of positive 

 and negative hallucinations. For instance, supj)Ose a short- 

 sighted person does not accurately see some one in the dis- 

 tance ; the sensations he receives may suggest to him that 

 he sees some one else. This belief will lead him to sup- 

 press those sensations which do not, and to add those which 

 do, agree with his memories of the person he thinks he 

 sees ; so that the illusion becomes rounded off and perfect. 



(It may be remarked that some English ps^^chologists 

 extend this use of the w^ord " illusion " so as to include 

 what has been called here " hallucinations with a point de 

 repere,^^ and which, it may have been noticed, have this in 

 common with " illusions," that actually they are the sum of 

 positive and negative hallucinations.) 



Senses. Without suggestion. — It would appear that, as 

 a rule, no alteration takes place in the acuity of the senses 

 in either the pre-somnambulistic or somnambulistic stage, 

 unless some suggestion be made. It is, however, somewhat 

 difficult to be certain, insomuch as in testing this some 

 suggestion may involuntarily be given, and accepted by the 

 " subject " owing to his increased suggestability. 



With suggestion. — As was stated above, " subjects " 



