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.
From the enormous work which has been done on cancer with the microscope and the test tube, it would seem sometimes that research workers have become somewhat myopic, and not farsighted enough to recognize the true value of statistical studies and clinical observations. In these lectures we have attempted to make a brief synthetic study of some of the work which has been done in connection with cancer, and from this we believe that certain conclusions can be drawn; if these are correct and followed, it is hoped that much more can be accomplished in regard to the prophylaxis and cure of this more than threatening, fatal malady. In order that you may hold clearly the points which have been made I want to give you a synopsis or conclusions of them, as they have been brought out in this and preceding lectures.
1. Cancer is but a deviation from the normal life and action of certain of the ordinary cells of the body, which, for some as yet unexplained reason, take on an abnormal or morbid action; with this there is a continued tendency to a malignancy which invades contiguous tissue, and in the end tends to destroy life.
2. There is some reason to believe that this action first takes place in what are known as “embryonic rests,” or pre-natal, wrongly placed tissue elements, which, however, are now shown to exist in every one, in many localities: but the reason why they take on this malignant action, and form cancer, has not been satisfactorily explained.
3. Cancer is not wholly due to traumatic causes, although those play a not inconsiderable part in its occurrence in certain localities and cases.
4. It is pretty conclusively decided that cancer is not caused by a micro-organism, or parasite.
5. It is also known clinically and experimentally that it is not contagious.
6. Nor is it hereditary in any appreciable degree.
7. Occupation has not any very great influence on the occurrence of cancer, although it is more frequent in some pursuits than in others.
8. Cancer is not altogether a disease of older age, although its incidence is greatly increased with advancing years.