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PIONEERS OF EVOLUTION, 



structure, the nervous system, under which objects 

 are seen and sensations felt when no corresponding 

 impression has been made through the medium of 

 the senses. When the nervous system is out of 

 gear, voices, whether divine or of the dead, may be 

 heard; and actual figures may be seen. A mental 

 image becomes a visual image; an imagined pain 

 a real pain, as the great physiologist, John Hunter, 

 testified when he said, " I am confident that I can 

 fix my attention to any part until I have a sensation 

 in that part." Shakespere portrays the like condition 

 when Macbeth attempts to clutch the dagger where- 

 with to stab Duncan: 



There's no such thing ; 

 It is the bloody business which informs 

 Thus to mine eyes. 



This abnormal state, which sees things having no 

 existence outside the " mind's eye," is no respecter 

 of persons; the savage and the civilized are alike 

 its victims. It may be organic or functional. 

 Organic, when disease is present; functional, through 

 excessive fatigue, lack of food or sleep, or derange- 

 ment of the digestive system, causing the patient, 

 as Hood says, "to think he's pious when he's only 

 bilious." Under such conditions, hallucinations of 

 all sorts possess the mind; hallucinations from which 

 the true peptic, who, as Carlyle says, " has no sys- 

 tem," is delivered. Only the mentally anaemic, the 

 emotionally overwrought, the unbalanced, and the 

 epileptic, are the victims, whether of the lofty illu- 



