462 PHYSIOLOGY CHAI-. 



the assumption that the sound necessary to arouse the 

 must he in direct relation to the profoundness of sleep. This 

 research was repeated by Mpnninghoff and I'ieshergen, Michelson, 

 Koiuer, and Weygand. They distinguished a normal type of 

 sleep, which reaches its maximum after about an hour, then 

 becomes gradually less profound, and finally rises again towards 

 morning, from an abnormal, neurasthenic tt/pf. which reaches its 

 maximum later and decreases more slowly. As regards the value 

 of these researches De Sanctis pointed out that sleep is not equally 

 susceptible to auditory stimuli in all subjects, and that sleep of 

 the auditory sense is not coextensive with general sleep. 



Waking is usually a spontaneous or automatic act, but may 

 also be determined and provoked. This occurs either because we 

 have slept enough, after the habitual eight hours of repose, or 

 because a sudden external stimulus or certain internal sensations 

 (hunger, thirst, cold, and those due to an uncomfortable posture, or 

 the desire to micturate, or the emotion produced by certain 

 dn-ams) interrupt sleep, or because we have previously determined 

 to wake at a certain hour. Many people succeed in waking 

 approximately at the hour they decide on, and are never more 

 than fifteen minutes out. 



Tschisch, in methodical researches on prearranged waking, 

 found that he invariably awoke before the hour decided on 

 ii'-vor later. Vaschide's investigations showed that sleep under 

 these conditions (sommeil expectatif) differs from ordinary sleep ; 

 it is more restless, and troubled by curious dreams. We 

 have already discussed the psychology of prearranged waking 

 (p. 453). 



The psychical phenomena of waking are not fundamentally 

 different from those of nascent consciousness after syncope, 

 described by Herzeu (su^tra, p. 444). The gradual passage from 

 sleep to waking was aptly defined by Buffon as " a second birth." 

 In the briefest possible time w r e recapitulate all the phases of the 

 psychical development of the new-born infant and the babe. 



The activities of the organs of vegetative life are not suspended 

 during sleep ; somnus labor visceribus motus in somno intra 

 vergunt, wrote Hippocrates. It is worthy of note that while the 

 chemical processes of digestion proceed actively, the intestinal 

 movements and peristalsis are diminished. Digestion, particularly 

 after an abundant meal, usually produces drowsiness, due, some 

 say, to the congested state of the abdominal viscera which 

 produces a corresponding ischaemia of the brain. On post-mortem 

 examination of persons who died in the night the food is found 

 more digested in proportion to the time that has elapsed since the 

 last meal which sometimes affords medical evidence as to the 

 hour of a violent death. Assimilation during sleep appears to be 

 favoured by the resting state of all the organs of animal life. 



