Until recently it has not been possible to speak with assurance concerning the influence of heredity on the occurrence of cancer; the evidence at hand has been of such an unsatisfactory character that the validity of whatever conclusions were drawn was always open to question. Numerous attempts to secure information by studying general mortality statistics, hospital populations or isolated clinical observations have led to contradictory results, as they were bound to do from the inherent errors in the data obtained from such sources. Furthermore, until within a comparatively short time, we had no definite knowledge of the principles of heredity itself, and this ignorance foredoomed to futility any speculations on the subject.
It so happens that the year 1900 saw the rebirth of two unrelated discoveries which, together, have led to an entirely new outlook on the problem, for they placed for the first time on an experimental basis the
WELLS HG. THE INFLUENCE OF HEREDITY ON THE OCCURRENCE OF CANCER. JAMA. 1923;81(12):1017-1021. doi:10.1001/jama.1923.26510120005012