Dr. James B. Murphy demonstrated that accompanying cancer grafts on immune animals there occurs a general increase in the circulating lymphocytes and hyperplasia of the lymphoid tissue. When the lymphoid tissue of immune animals was destroyed, the immunibility was annulled. Two methods of increasing the lymphocytes have been found, namely, diffuse small doses of X-rays, and dry heat. Mice with lymphocytosis induced by these agents show Increased resistance to replants of their own tumors. The results afford ground for hope of human application. (Reported in _Scientific American Monthly_, January, 1920, page 96.) It has been found that actively growing tissue, whether normal or pathological, is the most susceptible to X-rays, and it is comparatively easy to sterilize a number of species of animals without otherwise injuring them. (Prof. James W. Mayor, _Science_, September 23, 1921.) C. R. Bardeen found that X-rays prevent worms from regenerating lost parts. Observations of the effect of exposure to X-rays on the fertility of animals were described in a paper by Prof. L. H. Snyder of the North Carolina College of Agriculture. Exposure of male rats to X-rays, he said, had rendered them sterile at the end of two months, the animals regaining fertility when no longer subjected to the rays. If not handled with due caution and skill, X-rays may do more harm than good, provoking malignant growths as well as retarding their development. As early as 1911, Otto Heese published a record of 54 cases of cancer caused by means of improper handling of these powerful rays. In the early days of X-ray therapy the nature and effects of these radiations were wholly unknown. Operators did not hesitate to test and adjust their tubes by throwing the shadow of their hands on the flouroscope. X-rays do not make objects visible to the human eye, and to see the effects of them it is necessary to interpose a special screen between the eyes and object through which the X-rays are to penetrate. The cardboard screen is coated with a fluorescent substance, such as barium-platinum-cyanide, or calcium tungstate. This screen is best placed in one end of a black wooden or pasteboard box, against the other end of which the eyes are placed when in use. This screen under the influence of X-rays becomes luminous and enables one to see shadows or silhouettes of objects of denser material interposed between the eyes and the X-ray tube, when the tube is in operation. CHAPTER III MARTYRS TO RADIOLOGY It was not until several years after the discovery of X-rays by Roentgen, in December, 1895—after operators had been severely burned in laboratories and hospitals all over the world, and surgeons and physicians began to compare notes, that the pathological effects of X-rays were discovered and understood. Says John Macy (in his memorial volume on Walter James Dodd, heroic victim of 50 separate operations due to X-ray burn):