Some time ago Lange and Boyd1 showed that intravenously injected fluorescein can be made visible immediately on its arrival in the small blood vessels of the skin and the mucous membranes if a beam of long wave ultraviolet radiation is directed on a given area in a dark room. On this basic principle it seemed that the procedure might aid in establishing the diagnosis and prognosis of peripheral vascular diseases. Certain conditions, however, had to be studied before the test could be introduced for general use in various problems concerning vascularity of tissues.
PHYSICAL AND PHARMACOLOGIC BASIS
Fluorescein is resorcinolphthalein. It has an extremely small molecule, since its molecular weight is 332. It is a brown substance which is soluble in an alkaline solution. While the sodium salt is freely soluble in water, it is optically much less active than fluorescein (table 1). Accordingly, it is inadvisable to use sodium