9A KANSAS CITY REVIEW OF SCIENCE. 
POR EIGN COmn 2S: OND ane 
SCIENCE LETTER FROM PARIS. 
June 18, 1880. 
French alienists consider ‘‘hallucination” as a perception without an object, 
and ‘‘illusion” as a real perception falsely interpreted. In both cases the result 
is due to united physical and mental causes, that is, the commencement is a 
physical sensation. An ancient and famous philosopher maintained that the en- 
tire universe was only a gigantic hallucination. People are not necessarily ill or 
mad because laboring under an illusion; at a distance a square tower may ap- 
pear round, owing to perspective modifying the apparent forms of objects. In 
the eyes of a maniac, linen suspended from a line becomes hanging corpses; im- 
ages floating in the air, appear balloons directed by aeronauts. Laseque defined, 
that illusion is to hallucination, what slander is to calumny. With lunatics at 
least, it is the ear which occupies the first réle in cerebral troubles; they hear the 
sound of footsteps as of a person walking in another room; or some musical 
notes, musketry fire, or the reports of cannons. But there is an abyss between 
the pa'ient who hears only sounds, and him who listens to words, the latter at first 
in monosyllables, then becoming phrases, and finally sentences, till the afflicted 
indulges in replies, and terminates by believing he is in presence of a distinct 
personality who encroaches on his existence. Such is the meaning of the ‘‘pos- 
sessed” of the Middle Ages, and later of the seventeenth century. It is thus 
that the exorcists charged to deliver the Ursulines of London from the diaboli- 
cal spirits of which they were possessed, became in several instances themselves 
the victims of the epidemic. Sight also plays a conspicuous rdle in hallucina- 
tions, producing alcoholic night-mares, and unceasing terrifying visions. The 
sensitive apparatus is composed of extremities which receive the impression; the 
tube which transmits it, the ganglions which receive and condense it, then those 
cellules of the hemisphere of the brain which perceive it, and that represent 
matter in its highest expression of relationship with intellectual fuctions—and 
where alone phenomena can be judged. The deaf, strange to say, suffer from 
hallucinations of hearing, as well as the blind from those of seeing. Certain 
physiologists maintain, that we ought never to forget anything, because the cere- 
? 
bal cells always remain filled with impressions, though in a latent state, and that. 
there is a mystical power, independent of our will, at work, ready to call up these 
forgotten sentences. During a conversation, we may suddenly forget a name or 
date; next day when the circumstance has passed away, the wanted name or 
date will surge up. What is that automatic, mysterious secretary that has been 
working for us independent of our will? J. J. Rousseau, when conversing, 
was heavy and embarrassed, and it was only on arriving at the foot of the stair- 
case that he discovered the witty reply that he ought to have made in the draw-_ 
