When physiologic sodium chloride is injected into the skin of a normal person, it produces a distinct, elevated blanched area, from 1 to 1.5 cm. in diameter, at the point of injection. The hair follicles are distinctly visible on the center of this area. As the saline solution is absorbed, this elevation becomes less palpable; it finally disappears in about sixty minutes in adults and somewhat more quickly (from thirty to fifty minutes) in infants.
It was found by McClure and Aldrich1 that the disappearance time was much diminished in a group of children with edema as compared with that in a group of control cases; furthermore, that the greater the degree of edema, the shorter the disappearance time and vice versa. The authors showed that by the use of the test, the occurrence of edema might be foretold before it was demonstrable clinically. Moreover, they found that an