One rainy morning in April, Luther Trant sat alone in his office. On his wrist as he bent closely over a heap of typewritten pages spread before him on his desk, a small instrument in continual motion ticked like a watch. It was for him an hour of idleness; he was reading fiction. And, with his passion for making visible and recording the workings of the mind, he was taking a permanent record of his feelings as he read.

The instrument strapped on Trant’s arm was called a sphygmograph. It carried a small steel rod which pressed tightly on his wrist artery. This rod, rising and falling with each rush of the blood wave through the artery, transmitted its motion to a system of small levers. These levers operated a pencil point, which touched the surface of a revolving drum. Trant had adjusted around this drum a strip of smoked paper, the pencil point traced on its sooty surface, and a continuous wavy line which rose and fell with each beat of the psychologist’s pulse.