PREFACE Two years ago the present writer ventured to put forth a small book in which cancer was considered from quite a different standpoint from that commonly held by the profession and laity. The kindly reviews of the medical press indicated that, while this was antagonistic to accepted views, there was warrant for such an investigation, in view of the steadily increasing mortality from cancer all over the world, under the present mode of purely surgical treatment. In these two years there has been very active study of cancer together with a campaign of education in regard to the desirability and necessity of operating very early in the disease, and consequently an increased surgical activity. In spite of all this, or possibly on account of it, the mortality from cancer during 1915 has been appreciably higher than the average yearly death rate during the preceding five years. It would seem, therefore, that there was increasing necessity for the study of the conditions which cause the disease, as found in the human system, rather than an increased study of pathological specimens and experimentation on animals. During these two years the writer has sought to understand the disease better by constant clinical observation in private and public practise and by wider acquaintance with literature, and has been only strengthened and confirmed in the views which were set forth in the former small book, and which he has held and practised for over thirty years. With some care he has prepared a second series of lectures which were given to practising physicians attending the regular Wednesday afternoon clinics at the New York Skin and Cancer Hospital in November and December, 1916, and which are now submitted to the profession at large. The reasons for presenting the medical aspects of cancer were given in the former volume, also the hesitancy I felt lest, from an imperfect carrying out of the necessary lines of internal treatment, harm might be done or time lost in which there might possibly be some gain from surgical treatment. But the more I have studied cancer in the living and dying subject, and the more I have tried to compass literature and analyze statistics, the more have I felt compelled to push forward a campaign of education in regard to the basic causes of the disease, ever with the thought of prophylaxis, by inculcating right living. It has been painful to me to present the mortality statistics in such an unfavorable light as is seen in the following pages: but truth is truth and truth must prevail.