In spite of the fact that the majority of cancer deaths occur because of lymphatic metastasis, the effects of radiation upon the lymphatic vessels are still imperfectly known. Essentially the question is: Is it possible to “seal” the lymph vessels by irradiation? In an attempt to answer this question a number of experiments were conducted at the Radiological Institute of the University of Modena during the last five years with 200-kv radiation, a cobalt bomb, and by a 15-Mev betatron. Rabbits and guinea pigs were employed as experimental animals, and, in addition, 30 human uteri were examined following irradiation and hysterectomy for cancer. The technics of examination included injection of latex in the lymph vessels followed by maceration of the tissues. The circulating lymph was studied by phase contrast microscopy. For study of the circulating lymph 40 guinea pigs were given whole-body irradiation with a 1,500 curie cobalt bomb for a dose of 7,500 r at one sitting. Lymph specimens were studied five an...