7 o6 THE POPULAR SCIENCE MONTHLY, 



" The lunatic, the lover, and the poet, 

 Are of imagination all compact: 

 One sees more devils than vast hell can hold ; 

 That is the madman : the lover, all as frantic, 

 Sees Helen's beauty in a brow of Egypt : 

 The poet's eye, in a tine frenzy rolling, 

 Doth glance from heaven to earth, from earth to heaven; 

 And, as imagination bodies forth 

 The forms of things unknown, the poet's pen 

 Turns them to shapes, and gives to airy nothings 

 A local habitation and a name." 



Or I might adduce the case of the great Protestant Reformer, Luther, 

 who is said I know not how truly to have thrown his inkstand at 

 the devil on one occasion ; at any rate the mark of the ink is still 

 shown on the wall of the chamber which Luther occupied. True or 

 not, there is nothing improbable in the story ; for Luther, though en- 

 dowed with great sagacity and extraordinary intellectual energy, enter- 

 tained the common notions of the personality and the doings of the 

 devil which were current among the people of his age. He pictured 

 him very much as a Saxon peasant pictured him. It was the devil, 

 he believed, who caused a great storm, and he declared that idiots, 

 the blind, the lame, and the dumb, were persons in -whom devils had 

 established themselves, and that physicians who tried to cure their 

 infirmities as though they proceeded from natural causes were igno- 

 rant blockheads who knew nothing of the power of the demon. He 

 speaks of the devil coming into his cell and making a great noise 

 behind the stove, and of his hearing him walking in the cloister above 

 his cell in the night ; " but as I knew it was the devil," he says, " I 

 paid no attention to him, and went to sleep." 



This, then, is one way in which hallucination is produced by the 

 downward action of idea upon sense. My illustrations of this mode 

 of production have been taken from sane minds, but the hallucina- 

 tions of the insane are oftentimes generated in the same way. A 

 person of shy, suspicious, and reserved nature, who imagines that 

 people are thinking or speaking ill of him or going out of their way 

 to do him harm, nurses his habit of moody suspicion until it grows to 

 be a delusion that he is the victim of a conspiracy ; he then sees evi- 

 dence of it in the innocent gestures and words of friends with whom 

 he holds intercourse, of servants who wait upon him, and of persons 

 who pass him in the streets ; these he misinterprets entirely, seeing in 

 them secret signs, mysterious threats, criminal accusations. It may 

 be pointed out to him that the words and gestures were perfectly 

 natural and innocent, and that no one but himself can perceive the 

 least offense in them ; his belief is not touched by the demonstration, 

 for his senses are enslaved by the dominant idea, and work only in its 

 service. Sometimes an insane patient, who tastes poison in his food 



