"Lawrence had tablets of sodium chloride made up containing extremely small percentages of Na²⁴. During lecture demonstrations, he would swallow one of these tablets and then, holding his hand over a Geiger-Müller counter, demonstrate how the radiosodium reached his hand following absorption in the stomach and circulation via the blood stream. The counting rate exhibited by his hand also declined during the lecture, demonstrating both the radiologic and the biologic decay times."