A Bioanalytical Contribution to the Problem of Sleep and Wakefulness

Johannes Müller, the great physiologist and teacher of Helmholtz, Dubois-Reymond and Ernst Brücke—to mention only the greatest names among the pleiad of his disciples—is said to have coined the aphorism: Physiologus nemo nisi psychologus.

There is probably no better proof of this saying in the history of physiological research than the striving of physiologists to understand the problem of sleep. In order to illustrate their almost complete failure with this problem—which has for many centuries been a subject of persistent research—I quote the statement of a witness who is the more dependable since he is not compromised by psychology. The physiologist Kleitman of Chicago has studied the problem of sleep for twenty-two years—mostly experimentally—has contributed numerous papers to it, and has recently published a book of more than five hundred pages entitled Sleep and Wakefulness. In this work he enumerates no fewer than one thousand four hundred and thirty-four references, all of them published since 1912. His last chapter begins with the words: 'It is commonly stated that we know nothing or practically nothing as to what causes sleep'.

Johannes Müller's aphorism was fully verified by Freud at the turn of the century and in subsequent decades when he emphasized the participation of psychological factors in sleep, thus characterizing it as a psychobiological phenomenon. This was a revolutionary step. Not only did it lead to the abolition of the prevailing concept of sleep, but it opened up a path for further research. In a little paper called Instinct