It is of great importance, for scientific reasons and for the more limited purpose of safeguarding against possible dangers in X-ray therapy, to discover whether there may be conditions which facilitate the production of tumours by X -rays. Some light has already been thrown on this problem. Lacassagne and Vinzent (1929) (1933) caused inflammation in the groins of rabbits by the subcutaneous injection of
Streptococcus caviae
. The lesions in some of these rabbits were submitted to X-radiation, the dose in each instance being about 600 r. Such doses had a beneficial effect on the infective lesions, but sarcomas developed in five of the twelve survivors at the sites of irradiation. In a later experiment non-infected inflammatory lesions, produced in rabbits by the subcutaneous injection of sterile diatomaceous earth, were exposed to X-rays, the dose being 600 r. as before. Two of these rabbits, at the end of 22 and 34 months respectively, were dead with malignant tumours at the site of irradiation (Lacassagne 1933). Similar doses of X-rays given to rabbits in the absence of inflammatory lesions did not induce tumour formation (Lacassagne 1936). Since a total of 600 r. is well within the limit of dosage used for therapeutic purposes in man, it seemed desirable to carry out further experiments of this nature. Experimental Technique Non-infective foci of inflammation were caused in twelve young adult rabbits as follows: 3 c. c. of olive oil containing 10% of finely powdered silica were injected subcutaneously in the right groins. Four days later, as no distinct swellings were present, the injections were repeated, 2% of oleic acid having been added to the olive oil. On the following day 7 c. c. of a suspension of kaolin (10% in water) were injected into the same sites. Three days later obvious swellings were present. Each rabbit was anaesthetized with “Evipan” and the swollen tissues were exposed to a single dose of 600 r., the rest of the rabbit being protected by a shield of lead. The conditions of irradiation were— 250 kV, 4 mA, filter 0·5 mm. Cu, time approximately 23 min.
ROENTGEN RAY INTOXICATION
