I have tried to make it plain that metabolic errors, inducing a vitiated blood stream, are the basic cause of the aberrant action in the cellular elements of the body which may ultimately lead to malignant disease; and I have tried to show that there are many elements connected with modern so-called civilization which conspire to effect this end. I have quoted many who were well acquainted with cancer, who believed that luxurious living, which includes much animal food, coffee and tea, and alcohol, with indolence or want of sufficient muscular activity to burn up the waste products, and the persistent neglect of hygienic laws, should be placed first among the causes of cancer: but I have also mentioned that the refining and preparation and cooking of food prevented a proper supply of the mineral and other elements of nutrition, and also that nervous influences could so disturb the action of the organs of the body that they could not perform their functions perfectly in the elaboration of nutritive material, etc. But I cannot go over again all the matter already given in these lectures, and only mention these to remind you that there is no one single cause of cancer, and consequently that its prophylaxis and cure can never be found in any one single remedy; hence I can never believe in the sole use of thyroid, much less in the idea that sero-therapy can overcome a disease dependent upon the continued operation of so many causes; and still less can I believe that the mere cutting out of an already diseased portion of the body is the proper and only means of overcoming such a malady as cancer. I have acknowledged that local irritation of many kinds may be the proximate cause for the development of a malignant tumor in any particular locality, as Ewing has so clearly shown in his excellent resumé on pre-cancerous lesions; but I have also contended that we should withal look into and overcome the cause; why, when once started by local injury the cells should pursue such a progressive, aggressive, and invasive course; and this is found, I believe, in the disturbed character of the fluids which provide them with nourishment for their abnormal growth. From this study of cancer in regard to its nature, frequency, geographical distribution, metabolism, dietetic relations, medical treatment, and clinical considerations, what conclusions can be drawn? Have we solved the problem of cancer? Far be it from us to make any such claim. Scientific research and study must still go on in the laboratory, but clinical research and study, with laboratory work, on the human subject, which have not been hitherto sufficiently cultivated, should be pushed, so that by a mass of carefully recorded observations the truth or falsity of what has been here quoted and said may be refuted or confirmed.