Any one who has been thinking much for several days about a problem is likely to wake up with the thought that he has dreamed a solution of it, though unfortunately the solution has not remained in his memory. It seems as if a communication has been made to him during sleep. I have discussed dream life with many men engaged in serious work, and practically all of them confess to such experiences. Preoccupation of mind with a subject during the waking hours leads to at least some occupation of mind with the same subject during sleep. This unconscious occupation must often require rather strenuous attention, exhausting nutrition, using up nerve force and hampering the rest that is so important for tired human nature. [Footnote 17] [Footnote 17: A number of poetic products of dreams are in our literature, some of them interesting for more than their curious origin. Dr. S. Weir Mitchell, in his latest volume of poems, "The Comfort of the Hills," made an interesting contribution to the psychology of dreams by publishing two poems which were composed by him while asleep. The little poem, "Which?" has all the curious alliterativeness and frequent rhyme that is so likely to be noted in expressions that come during sleep, or just as we awake. The other is more like a somnambulistic effort. What we might suggest here is that the habit of poetizing during sleep would surely be dangerous to any one less eminently sane than their author. We give them as curious examples that will interest patients who complain that their dreams are too vivid. APRIL FIRST Come, let us be the willing fools Of April's earliest day. And dream we own all pleasant things The years have reft away. 'Tis but to take the poet's wand, A touch or here or there, And I have lost that ancient stoop, And you are young and fair. Ah, no! The years that gave and took Have left with you and me The wisdom of the widening stream; Trust we the larger sea. WHICH? Birth-day or Earth-day, Which the true mirth-day? Earth-day or birth-day, Which the well-worth day? For further details on this subject, see the chapter on Dreams.]