Dr. M. Allen Starr, the distinguished nerve specialist of New York, writes me that there are several explanations of the cause of such depression. He is of the opinion that those who are depressed from melancholia when they wake in the morning, are probably suffering from a toxic condition of the blood which originally produced the melancholia. This toxin, or poison, is resisted by the nervous system when it is well nourished, but has a greater effect when the nervous system is poorly nourished. He says that there is a general consensus of opinion that, during sleep, the blood vessels of the brain are contracted slightly so that the amount of blood going into the brain during sleep is less than during the waking hours. This was proved many years ago by Professor Mosso of Turin, by a series of experiments which are conclusive. When blood vessels are contracted, and less blood is going to an organ, the nutrition of that organ is less actively maintained. Hence, if a person has poison in the system, it is less restricted during sleep, has a greater opportunity to attack the nerve-cells, and thus to prevent the nutrition which is essential to the feeling of general comfort. That is the theory on which we physicians explain depression on awaking after sleep in melancholia. What is true of melancholia is probably true also of fatigue conditions and irregular conditions of health, many of which are dependent upon the existence in the blood of substances detrimental to health, either the products of indigestion or the poisons of disease. This theory explains the conditions in which a person not actively ill may awake from a sleep in a state of depression. (See Appendix A.) Prof. Edward M. Weyer in reading the sheets of this book suggests another tentative explanation of depression upon waking: if we consider the nerve cell as stored with energy, then, if the store is maintained at normal, it is in a healthful state. The supply fluctuates somewhat during the day, but in the melancholic person it does not rise to normal even after good sleep: the less amount of carbonic acid gas eliminated during sleep leaves the system on waking at the mercy of that poisoned gas and of the chronically low nervous energy. CHAPTER XXXII THE LOVE THAT IS PEACE Sweet gate of life, sweet type of death— Come, Sleep! DORA READ GOODALE. Many persons lose sleep because of their love for others, as the lover who sighs and tosses, dreaming, asleep or awake, of the beloved. The mother loses sleep thinking of the child with its little worries and problems, its willfulness or its frail health. There is always some cause that seems to her reasonable ground for worry. The father, too, plans for the future of his son, and lies awake to map out a life for another human being, as if that being were a puppet and his father held the strings by which it could be moved in his hands.