666 THE POPULAR SCIENCE MONTHLY. 



more pronounced expressions of lunacy, but are unable to trace the 

 expressions to their relating causes. 



To have even a moderate understanding of insanity, it is necessary 

 to clearly comprehend the nature and import of " illusion," " hallucina- 

 tion," and " delusion " — which, when they exist, are of so much im- 

 portance that some would fain have us believe that the possession of 

 any one of these symptoms is sufficient to make genius and insanity 

 " a little more than kin, and less than kind." 



When a person sees, hears, smells, tastes, or feels an object, but 

 perceives it to be what it is not — as when a tree becomes a man, and 

 the murmuring wind his voice — an illusion exists ; a real sense-impres- 

 sion is wrongly interpreted by the perceptive centers, and hence the 

 perception does not correspond with the external object. 



Hallucination originates within the brain, and is the perception of 

 that which has no real existence ; indeed, so purely subjective is it, 

 that the senses have no agency in its production. Under conditions 

 of concentrated attention, ideas, feelings, and sense-perceptions, are 

 marshaled into consciousness with as great distinctness as if they were 

 the products of external objects, rather than that of subjective condi- 

 tions alone. This comes from the fact that the sense-centers are in- 

 fluenced by impressions received independent of their source. Its 

 function is to transform impressions into conscious sensations, and 

 hence an idea or emotion, when directed in a special way with per- 

 sistent, concentrated force, may so impress the sensorium as to cause 

 it to project into consciousness sensations which seem to come from 

 objects in the external world. I can not tell how this is done, neither 

 can I tell how it is done when impressions come from without. The 

 facts we know, but the secrets of transformation elude us. The brain 

 constructs new forms, but conceals the methods of imagination by the 

 shadow of unconsciousness. 



Ajax becomes enraged because the arms of Achilles are given to 

 Ulysses, and in his wrath he sees animals as Greeks and assails them 

 as if Ulysses and Agamemnon themselves were before him. Talma 

 intensified his emotions and his dramatic effect by the illusive specters 

 of his mind. Spinoza beheld with great distinctness the disagreeable 

 image of his dream a long time after sleep was gone ; and Niebuhr, 

 when describing the scenes of his travels, would see all rise before 

 him in " all the coloring, animation, and splendor of Nature." Multi- 

 tudes have been at times subject to the same false perceptions ; as 

 when the soldiers under Constantino saw the cross in the sky bearing 

 the inscribed words, "In hoc signo vinces" ; or when the army at the 

 battle of Antioch, excited and superstitious, saw the saints — George, 

 Demetrius, and Theodosius — descending through the clouds of heaven 

 to their support. 



The consummate skill of Shakespeare in portraying the different 

 phases of false perception, and his power of psychological analysis, are 



