No phase of modern science so closely touches the welfare of humanity as the studies which concern the prevention of disease. Up to a very recent period, well within the lifetime of many now living, practically the entire energy of the medical profession was given up to the treatment of human ailments, with an almost complete disregard of problems of prevention or studies of origin. To-day, in great measure, all this has been changed, and the importance of preventing disease has come well to the front. It is permissible to doubt whether the "cure" of any of the principal infectious diseases is likely to be so thoroughly accomplished as to eliminate it as a cause of mortality, and we may regard with greater promise attempts to discover the mysterious causes of our diseases, and the best methods by which their spread may be prevented. It is certainly a great gain that during the last hundred years mankind has learned that deliverance must come through human activity, and has ceased to regard typhoid or consumption as a dispensation of Providence. For the conquest of some of the principal maladies affecting the human race at the present time I have long questioned whether the laboratory for experimentation upon animals offers the opportunity for the surest results. The average man has his attention fixed upon mysterious researches which are being carried on in this or that "Institute"; rumours of impending discoveries and almost certain cures are published far and wide; and gradually one gets the impression that notwithstanding abundant disappointments, it is only by yet more vivisection that the mystery will be solved. Is this a valid conclusion? In many cases, might not scientific research have a better chance to discover the secret of origin were it directed into other channels? I propose to suggest one method of scientific research with which vivisection is in no way concerned--an investigation into the cause of one of the most terrible and most threatening of human maladies--cancer, or malignant disease. The subject is a vast one. Within the limits of a few pages it cannot be treated with any approach to the completeness which its importance demands. The utmost that can now be attempted is the suggestion of certain lines of research independent of animal experimentation, which, if carried out with completeness, might lead to results of incalculable benefit to humankind.