INTRODUCTION The Combination of Oil with Iodine. —The value of iodized oil as a diagnostic agent in diseases of the lungs depends on two properties: the opacity to the roentgen ray, owing to the high iodine content, and the nonirritating quality of the substance. Oils combined with iodine or bromine were originally used as therapeutic agents in medicine. They were administered by mouth and by subcutaneous injection. The conception of using such a combination was associated with the empiric use of cod liver oil, the beneficial effects of which were attributed to the richness of the drug in iodine. It was also noted that iodides, valuable medicaments by themselves, were particularly useful when combined with fats. Moreover, the tolerance to iodine when combined with lipoids was considered higher than that to other preparations, such as sodium or potassium iodide. It has been shown experimentally that fat which has absorbed about