588 ANNUAL, KEPORT SMITHSONIAN INSTITUTION, 1911. 



Or is our consciousness discontinued? If it be not continuous, how 

 can we account for that deep feeling that we have of the unity and 

 continuity of our personality? 



Moreover, how do we distinguish the dream from the reality? 

 Descartes says : 



How many times at night have I thought that I was in a certain room, that I was 

 clothed, that I was near the fireplace, although I was undressed and in my bed! It 

 is plain to me at this moment that it is not at all with sleepy eyes that I behold this 

 paper; that this head that I nod is not at all drowsy; that it is with design and delib- 

 erate purpose that I extend this hand and feel of it. What happens to me in my sleep 

 is not near so clear and distinct as this. 



We certainly distinguish far more clearly the incidents of our 

 daily life than those of our dreams. Yet, after all, who has not asked 

 himself on waking up whether these thoughts were visions or the 

 reality ? And how can he be sure which is correct ? This explains the 

 perplexity of Pascal when he says : 



Who knows whether that other part of life when we think we are awake is but 

 another kind of sleep, a trifle different from the first, to which we are aroused when 

 we think we are asleep? 



These two conceptions of a continuous personality and of the reality 

 are subjects of psychological studies relative to sleep. Not only do 

 psychologists observe these in respect to themselves but their vari- 

 ations in other persons. And they have demonstrated some curious 

 phenomena. Though most men have a distinctive and strong person- 

 ality, there are those in whom personality is disorganized, and some 

 have come to have two absolutely independent personalities, as the 

 hysterical individuals observed by MacNish, Azam, and others. 

 Though the majority of men clearly distinguish the genuine from 

 dreams, it is equally true that some can not make this distinction and 

 take their dreams for realities and realities for dreams. Disorders of 

 the personality and the perception of the reality are, however, patho- 

 logical conditions and their study is altogether more within the 

 domain of the physician than of the psychologist. The physician 

 devotes himself to numerous problems pertaining to sleep. Aside 

 from the hygiene of normal sleep which is within his jurisdiction, he 

 must also consider its disturbances, such as hysteria and various con- 

 ditions more or less comparable to sleep, as hypnotism, lethargy, 

 anesthesia, coma, sleeping sickness, and the like. 



Hysteria is an illness that most disturbs sleep. Besides the con- 

 ditions of disorganization of the personality and the loss of percep- 

 tion of the reality of which I have spoken, hysteria presents other 

 disorders, either provoked, as in hypnotism, or involuntary, as in 

 lethargy. A discussion of these phenomena would be very interest- 

 ing, but it would take too long a time. 



