The basis of this little volume is a paper on Insomnia, published in the New York Medical Journal in May and June, 1865. This was subsequently enlarged and published in a separate form, under the title “Wakefulness, with an Introductory Chapter on the Physiology of Sleep.”

The very favorable reception which it met with in this country, in Great Britain, and on the Continent, from the medical press, the profession, and the public generally, led to the exhaustion of a large edition in a few months.

The present issue was announced nearly two years ago, and the printing begun. Increasing professional duties have, however, prevented me bestowing that continuous labor upon it which was desirable, and hence the publication has been long delayed. My apologies therefore are due, first, to my excellent and dear friend, the senior member of the house of J. B. Lippincott & Co., whose patience I know has been severely tried, but who has scarcely reproached me for my neglect; and second, to that portion of the public which has been kind enough to make repeated inquiries relative to the appearance of this monograph, and which I trust will not be disappointed, now that it is really published.

162 West 34th St., New York,
July 10th, 1869.