In this paper the author records the results of a series of elaborate experiments showing the condition of mental function during prolonged abstinence from food. The experiments were made on six individuals; the period of fasting generally ranged between 12 and 36 hours; in one instance it was extended to 48, and in another to 72 hours. In some of the experiments water was withheld as well as food. The psycho-physical tests employed were those current in Kraepelin's laboratory, a few modifications of detail being introduced in some of them. One new method—Griesbach's examination of the range of tactile sensibility—was also tried, but was found very unsatisfactory.