Physical work succeeded no better than intellectual; he endured the fatigue of butchers and wood-choppers, but he did not obtain their sleep.  Decidedly, bodily fatigue was worth no more than that of the brain.  It was worth even less.  At his table, plunged in his books, or in his laboratory over his microscope, he absorbed himself in his work, and, by the force of a will that had been long exercised and submissive to obedience, he was able to keep his thoughts on the subject in hand, without distraction as without dreams.  Time passed.  But when walking in the streets of Paris, in the deserted roads on the outskirts, by the Seine or Marne, his mind wandered where it would; it was the mistress, and it always dwelt on Madame Dammauville, Caffie, and Florentin.  It seemed as if the heat of walking started his brain.  When he returned in this state, after many hours of cerebral excitability, how could he find the tranquil and refreshing sleep, complete and profound, of the laboring classes who work only with their muscles?

Never having been ill, he had never examined nor treated himself:  medicine was good for others but useless for him.  With a machine organized like his he need fear only accidents, and until now he had been spared them; a true son of peasants, he victoriously resisted Paris life as the destroyer of the intellect.  But the time had come to undertake an examination and to try a treatment that would give him rest.  He was not a sceptical doctor, and he believed that what he ordered for others was good for himself.

The misfortune was that he could not find in himself any of the causes which resolve into insomnia; he had neither meningitis nor brain fever, nor anything that indicated a cerebral tumor; he was not anaemic; he ate well; he did not suffer with neuralgia, nor with any acute or chronic affection that generally accompanied the absence of sleep; he drank neither tea nor alcohol; and without this state of over-excitement of the encephalic centres, he might have said that he was in good health, a little thin, but that was all.

It was this excitement that he must cure, and as there are many remedies for insomnia, he tried those which, it seemed to him, were suitable to his case; but bromide of potassium, in spite of its hypnotic properties, produced no more effect than the over-working of the brain and body.  When he realized this he replaced it with chloral; but chloral, which should create a desire to sleep, after several days had no more effect than the bromide.  Then he tried injections of morphine.

It was not without a certain uneasiness that he made this third trial, the first two having met with so little success; and since it is acknowledged that chloral produces a calmer sleep than morphine, it seemed as if the latter would prove as useless as the former.  However, he slept without being tormented by dreams or wakings, and the next day he still slept.

But he knew too well the effects produced by a prolonged use of these injections to continue them beyond what was strictly indispensable; he therefore omitted them, and sleep left him.