But while early operation has improved surgical statistics, it has not contributed to our real knowledge of the basic cause of cancer, nor has it taught us why those lesions or “embryonic rests” will remain quiescent for years, or prove harmless in some individuals, while in others they become most formidable agents of destruction. For it is now recognized that these wrongly placed tissue elements are very common anatomical or histological accidents, indeed it is claimed that they occur and exist in every individual: and the removal of isolated “embryonic rests” which have developed into cancer, does not by any means prevent the transformation of other similarly misplaced cells into malignant disease, as the frequent recurrence of cancer after operation demonstrates. The same is true of the many and various forms of treatment other than surgical excision, such as deep acting caustics, and even the X-ray and radium, which like surgery, only remove the focus of possible systemic infection, and do not affect the basic cause of the complaint: this latter is being shown more and more, by scientific investigation and observation, to be associated with metabolic or chemico-physiological changes in the system, and evidence is accumulating that it is dependent upon them. All this leads thoughtful persons to inquire if there is not some deeper, fundamental cause lying back of the trouble, which should be reached and rectified by medical skill and acumen, something to do with the life or diet of a person which renders the tissues liable to take on malignant disease. So that a recent surgical writer on cancer states that “all study, whether clinical, pathological, or experimental, points to the fact that there is some underlying, hidden cause which leads to that aberration in the action of tissue cells which we call cancer,” ... a cause “residing in only the cells themselves or in some abnormal chemical constitution of the plasma bathing the cells, or in both of these possibilities acting together.” _Occupation_ has been questioned, but with most unsatisfactory results, for in some statistics which have been gathered cancer has been observed in those following all possible pursuits: and while laborers stood first on the list, clergymen stood fourth, while carters, threshers, and guides, who would be exposed to local injury, were at the bottom of a long list. It has been found, however, to be more frequent in trades or occupations in which the individual is most subject to the habitual abuse of alcoholics, as in bartenders, printers, etc.