LECTURE I CANCER AS A MEDICAL OR SURGICAL DISEASE In my lectures given here two years ago I considered, as far as I could in the time allowed, the nature of cancer,[1] and the evidence in favor of its being a medical rather than a purely surgical disease; and in order that the trend of what shall follow may be clearly understood, brief reference may be made to some of the principal points studied and developed in the preceding lectures. To this end I may restate the conclusions presented at their close, as developed in the lectures, perhaps with some alterations or additions which two years’ further study, observation, and treatment of cancer may suggest. 1. Cancer is but a deviation from the normal life and action of certain of the ordinary cells of the body, which, for some reason, difficult to understand, take on an abnormal or morbid action: with this there is a continued tendency in them to a malignancy which invades contiguous tissue, associated with a pernicious anemia which in the end tends to destroy life. 2. There is some reason to believe that this diseased action first takes place in what are known as “embryonic rests” or pre-natal, wrongly placed tissue elements. These latter, however, are now shown to exist in every individual in many localities, but the reason why at some particular time they take on this malignant action, and form cancer, has not yet been satisfactorily explained. 3. Cancer is _not_ wholly due to traumatic causes; although these may 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 microörganism or parasite; although various forms of these have been found in connection with the disease, and each has been claimed as the cause of cancer. 5. It is known clinically and experimentally that cancer is _not_ contagious. 6. _Nor_ is it hereditary in any appreciable degree; although certain rare instances have been reported in which such seems to be the case, and though some tendency in that direction has been demonstrated in certain strains of mice. 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 years; although its incidence is greatly increased with advancing age. 9. Cancer does _not_ especially belong to or affect any particular sex, race, or class of persons. It is, however, more frequent in females than in males, although of late years the proportion in the latter is steadily rising. 10. Cancer is _not_ confined to any climate, location, or section of the earth, but has been observed in all countries and climates, though with different frequency.