Insomnia and Other Disorders of Sleep

The regularly recurring incidence of natural sleep forms one of the most important subjects for physiological investigation. Were it an event of rare occurrence, it would excite a degree of astonishment and alarm equal to the agitation now experienced by the spectator of an ordinary attack of syncope or of epileptic convulsion. But, so completely does the recurrence of sleep harmonize with all the other facts of life that we are as indifferent to its nature as we are to every other healthy function of the body. It is only when the mind has undertaken a critical observation of the bodily and mental changes which accompany and condition the phenomenon that we begin to comprehend its wonderful character. Ushered in by a waning activity of body and mind that no effort of the will can long resist, nothing could more forcibly suggest the idea of approaching dissolution if, from the very earliest period of unconscious infancy, we had not been accustomed to the dominion of this imperious necessity. The remarkable likeness between the fading of consciousness in sleep and its extinction in death has, in all ages and among all people, arrested the attention of poets and philosophers of every degree.