424 MENTAL FUNCTION 



at least until death. On this principle, demanded by the continual 

 advancement of knowledge about the relations, of body and mind and 

 the nature of subconsciousness, coma might give a subconsciousness 

 down to its vanishing-point, perhaps, in death. In this state, however, 

 the conditions are different and abnormal, the essence of the state being 

 one of depression quite unlike the partial rest of sleep. 



Dreaming and its congeners somnambulism, etc., probably represent 

 the activity of certain more or less localized parts of the nervous system 

 separately. One could almost suppose they might depend on the vaga- 

 ries of the cerebral vaso-motion. The dream is an unusually vivid experi- 

 ence out of the subdued sleep-consciousness and, however long a time 

 its content may represent, lasts only a very short time. On the vaso- 

 niotor supposition it would be represented by a temporary dilatation of 

 some little region of the brain-capillaries, this congestion setting up for 

 a moment a more active metabolism and function. Similar in origin 

 may be the delirium so common when the vaso-motor .centers are apt to 

 be deranged, as in high degrees of fever. This notion as to the relation 

 of dreaming to local cerebral vaso-dilatation has never been demonstrated 

 and stands as an hypothesis allowable only where facts, except as to the 

 actual existence of cerebral vaso-motion, are lacking. 



It is a common experience that dreams are more or less dependent on 

 sensory stimuli. Thus, a child from whom the bed-clothes had fallen 

 dreamed of a frolic in a cold snowstorm, and an over-burdened stomach 

 readily transfers its load to the oppressive weight of a night-mare. Strains 

 or pressure on the nerves of the arm may readily give rise to indescribable 

 impressions of being overwhelmed by boundless waves of indefinite 

 matter. Such an experience forms, moreover, a striking example of the 

 widespread and absorbing mental impression which may come from the 

 stimulation of a single nerve-trunk. A common characteristic of the 

 dream-experience is its freedom from the restraints of common sense and 

 fact, not less than from other sorts of law: "In sleep a king, in waking, 

 no such matter." As men grow old they dream less and less, while 

 women maintain their early frequency in this respect and dream at all 

 life-periods more than do men (Heerwagen). According to Jastrow it 

 is " the vividness of the emotional background elaborated by the imagina- 

 tion that furnishes the predominant characteristic and tendency to 

 dreams." It is between the ages of twenty and twenty-five that dreams 

 are vividest, while in childhood they are by far the most numerous. 



Despite the evil dreams that come at times, sleep makes up much of 

 the happiness of life, just as it constitutes about one-third its duration. 

 Very few persons can work or feel well on less sleep than seven hours 

 daily, although six suffice some; rarely, after childhood is passed, does 

 one need over eight hours of rest. Sleep is indeed to the world's 

 multitude 



". . . the certain knot of peace, 

 The baiting-place of wit, the balm of woe, 

 The poor man's wealth, the prisoner's release, 

 Th' indifferent judge between the high and low." 



