21G 



ON THE EFFECTS OF CERTAIN MENTAL AND 

 BODILY STATES UPON THE IMAGINATION. 



BY LANGSTON PARKER, ESQ. 



V.— ON THE HALLUCINATIONS PRODUCED BY THE 

 IMAGINATION. 



Our present lecture relates to a mood of the Imagination distinct 

 from the three we have noticed in the previous discourses. Hal- 

 lucination is mistaken or diseased perception. It is the seeming 

 presence of that which does not really exist to the senses of a wak- 

 ing man. It may extend to all the organs through which we de- 

 rive ideas of the nature of things, but those of hearing and sight 

 are most commonly affected, and of these two most frequently the 

 latter. The Imagination derives all the materials from which it 

 compounds its extraordinary scenes from the sense of vision. Sight 

 is the most active, the most varied, and the most useful of all the 

 bodily senses ; most extended in its relations, and from which the 

 mind derives by far the greater part of its ideas. It has to do 

 merely with the surfaces of bodies, with their form, size, and co- 

 lour ; it is liable to misconception of these properties from many 

 causes — from distance, from the state of the atmosphere, and from 

 imperfection in the structure or functions of the eye itself. From 

 these multiplied sources are produced a variety of mistaken percep- 

 tions, termed optical illusions ; and from a number of causes of a 

 similar character the ear is misled, and conveys a mistaken and 

 false account to the brain. If these illusions be extended to the 

 other senses, of course they derange the operations of the mind 

 with regard to those properties of bodies which it is exclusively the 

 destiny of such sense to ascertain. But these are not hallucinations, 

 properly so called ; it is true they convey erroneous ideas, and 

 therefore may, in some measure, merit the term : but it is, as far as 

 I am acquainted with medical or philosophical language, and the ap- 

 plication of that language, exclusively applied to those illusions 

 where no physical agent is concerned in their production. As the 

 senses furnish the mind exclusively with all its ideas, and as this is 

 dependent for their truth upon the fidelity of its servants, so does 

 the mind by a reciprocal action, and by a mysterious property in- 

 herent in itself, direct the actions of the senses, and enable them to 



