DELUSIONS 443 



4. Delusions of Judgment.— The delusions of the 

 judgment, produced not by al)norm;il conditions of the 

 body, but by unusual or artificial combinations of sensa- 

 tions, or by suggestions of ideas, are exceedingly numer- 

 ous, and, occasionally, are not a little remarkable. 



Some of those which arise out of the sensation of touch 

 have already been noted. We do not know of any produced 

 through smell or taste, but hearing is a fertile source of 

 such errors. 



What is called ventriloquism (speaking from the 

 belly), and is not uncommonly ascribed to a mysterious 

 power of producing voice somewhere else than in the 

 larynx, depends entirely upon the accuracy with which 

 the perft)rmer can simulate sounds of a particular charac- 

 ter, and upon the skill with which he can suggest a belief 

 in the existence of the causes of these sounds. Thus, if 

 the ventriloquist desire to create the belief that a voice 

 issues from the bowels of the earth, he imitates with great 

 accuracy the tones of such a half-stifled voice, and 

 suggests the existence of some one uttering it by directing 

 his answers and gestures towards the ground. These 

 gestures and tones are such as would be pi'oduced by a 

 given cause ; and no other cause being apparent, the 

 mind of the bystander insensibly judges the suggested 

 cause to exist. 



The delusions of the judgment through tlie sense of 

 sight — optical delusions, as they are called — are more 

 numerous than any others, because such a great number 

 of what we think to be simple visual sensations are really 

 very complex aggregates of visual sensations, tactile sen- 

 sations, judgments, and recollections of former sensations 

 and judgments. 



It will be instructive to analyse some of these judg- 

 ments into their princi^iles, and to explain the delusions 

 by the application of these principles. 



5. The Inversion of the Visual Image. — Wlwn we 

 look at an external object, the 'ima(je of the object falls on 



